Deck 25: Current and Resistance

Question 1

A current of 0.500 A flows through an aluminum wire.The aluminum wire has a length of 2.00 m,a diameter of 0.0300 cm,and a carrier density of 6.02 * 10²⁸ electrons/m³.What is the electron drift velocity in the wire?

A)1.24 * 10^-8 m/s
B)1.84 * 10^-8 m/s
C)7.34 * 10^-4 m/s
D)1.84 * 10^-4 m/s
E)3.69 * 10^-4 m/s

Answer 1

7.34 * 10^-4 m/s

Question 2

The emf (electromotive force)is an

A)electric force vector.
B)electric force magnitude.
C)electric field vector.
D)electric field magnitude.
E)None are correct.

Answer 2

None are correct.

Question 3

A copper wire is connected across a battery.The direction of the current in the wire is

A)the same as the direction in which the electrons move.
B)opposite the direction in which the electrons move.
C)the same as the direction in which the protons move.
D)opposite the direction in which the protons move.

Answer 3

opposite the direction in which the electrons move.

Question 4

The equivalent resistance of the circuit shown if .If and ,what is the resistance of R₁?

A)11 $\varOmega$
B)2.9 $\varOmega$
C)4.1 $\varOmega$
D)5.2 $\varOmega$
E)7.7 $\varOmega$

Question 5

What is the equivalent resistance of the circuit shown if , ,and ?

A)7.7 $\varOmega$
B)10 $\varOmega$
C)56 $\varOmega$
D)61 $\varOmega$

Question 6

A copper wire has a diameter of d_Cu = 0.0400 cm,is 3.00 m long,has a resistivity of 1.72 * 10^-8 $\varOmega$ m and has a carrier density of 8.50 * 10²⁸ electrons/m³.The copper wire is attached to an equal length of aluminum wire with a diameter of d_Al = 0.0200 cm,and a carrier density of 6.02 * 10²⁸ electrons/m³.A current of 0.400 A flows through the copper and aluminum wires.What is the ratio of the current densities J_Cu/J_Al in the two wires?

A)0.25
B)0.50
C)2
D)3
E)4

Question 7

A current flows through an aluminum wire.The aluminum wire has a length of 2.00 m,a diameter of 0.0300 cm,and a carrier density of 6.02 * 10²⁸ electrons/m³.If the electron drift velocity is 1.84 * 10^-4 m/s,what is the current in the wire?

A)0.500 A
B)0.125 A
C)0.313 A
D)0.102 A
E)0.230 A

Question 8

A copper wire has a diameter of d_Cu = 0.0400 cm,is 3.00 m long,has a resistivity of 1.72 * 10^-8 $\varOmega$ m and has a carrier density of 8.50 * 10²⁸ electrons/m³.The copper wire is attached to an equal length of aluminum wire with a a carrier density of 6.02 * 10²⁸ electrons/m³.A current of 0.400 A flows through the copper and aluminum wires.If the ratio of the current densities the two wires,J_Cu/J_Al is 0.50,what is the diameter of the aluminum wire?

A)0.0800 cm
B)0.0283 cm
C)0.0200 cm
D)0.0565 cm
E)0.0400 cm

Question 9

A potential difference of 0.994 V is applied across a 170 m long,11-gauge wire copper wire.What is the current in the wire?

A)1.42 A
B)0.650 A
C)1.00 A
D)1.75 A
E)0.702 A

Question 10

A certain brand of hot dog cooker applies a potential difference of 120 V to opposite ends of the hot dogs and cooks by means of the joule heat produced.If energy of 62 kJ is needed to cook each hot dog,what current is needed to cook four hot dogs simultaneously in 1.5 min? Assume a parallel connection.

A)2.5 A
B)5.1 A
C)10 A
D)15 A
E)23 A

Question 11

If the current through a resistor is increased by a factor of 4,how does this affect the power dissipated?

A)It decreases by a factor of 4.
B)It increases by a factor of 4.
C)It decreases by a factor of 8.
D)It increases by a factor of 16.

Question 12

What is the resistance of a 15.0-m long,24-gauge (0.511 mm diameter)copper wire? The resistivity of copper is 1.72 * 10^-8 $\varOmega$ m.

A)0.315 $\varOmega$
B)1.26 $\varOmega$
C)1.52 $\varOmega$
D)0.534 $\varOmega$
E)1.89 $\varOmega$

Question 13

N identical resistors are connected in parallel.The resistance of one of them is equal to R.What is the equivalent resistance of all N resistors?

A)R/N
B)R
C)NR
D)None are correct.

Question 14

A resistor of unknown resistance and a 52-W resistor are connected across a 120-V emf in such a way that a 12-A current is observed in the emf.What is the value of the unknown resistance?

A)12.4 $\varOmega$
B)15.8 $\varOmega$
C)2.3 $\varOmega$
D)3.4 $\varOmega$
E)6.9 $\varOmega$

Question 15

A 22-gauge copper wire has a radius of 0.645 mm,is 5.00 m long,and has a resistivity $\rho$ = 1.72 * 10^-8 $\varOmega$ m.The maximum current for which this wire is rated is 0.920A.What is the maximum electric potential difference that may be applied to this wire without overloading it?

A)0.0605 V
B)0.112 V
C)0.242 V
D)0.342 V
E)0.561 V

Question 16

If the electric potential across a resistor is increased by a factor of 4,how does this affect the power dissipated?

A)It decreases by a factor of 4.
B)It increases by a factor of 4.
C)It decreases by a factor of 8.
D)It increases by a factor of 16.

Question 17

At a critical junction in a supercomputer,the current as a function of time is given as i(t)= 3t² -2t,where i is measured in milliamps and t is measured in seconds.How much charge passes through this critical junction during the interval 0 < t < 5.00 s?

A)28.0 mC
B)65.0 mC
C)100 mC
D)150 mC

Question 18

The current in an 11-gauge wire copper wire is 1.0 A and the wire is 170 m long.What is the potential difference across the wire?

A)1.01 V
B)1.43 V
C)0.994 V
D)0.852 V
E)0.701 V

Question 19

A potential difference of V = 0.500 V is applied across the length of a rectangular block of silicon (Si)with resistivity 8.70 *10^-4 $\varOmega$ m.The dimensions of the Si block are: width 1.50 mm;thickness 0.400 mm;and length L = 20.0 cm.You may assume that the current density in the Si block is uniform and that currents in Si obey Ohm's law.What is the resistance of this Si block?

A)92.3 $\varOmega$
B)362 $\varOmega$
C)78.4 $\varOmega$
D)290 $\varOmega$
E)452 $\varOmega$

Question 20

N identical resistors are connected in series.The resistance of one of them is equal to R.What is the equivalent resistance of all N resistors?

A)R/N
B)R
C)NR
D)None are correct.

Question 21

What is the battery current I_bat when the switch in the figure is closed?

A)8.0 A
B)9.14 A
C)1.09 A
D)12.5 A

Question 22

In the circuit shown,R₁ = 3 $\varOmega$ ,R₂ = 6 $\varOmega$ ,R₃ = 20 $\varOmega$ ,and $\varOmega$ = 12 V.Calculate the magnitude of current flowing through R₃ on the left branch of the circuit (marked with ☺).

A)0.5 A
B)1.0 A
C)0.25 A
D)2.0 A

Question 23

Which of the following has the smallest current flowing through it?

A)a 1-m long copper wire of diameter 1 mm connected to a battery of 10 V
B)a 0.5-m long copper wire of diameter 0.5 mm connected to a 5-V battery
C)a 2-m long copper wire of diameter 2 mm connected to a 20-V battery
D)a 1-m long copper wire of diameter 0.5 mm connected to a 5-V battery
E)All of the choices have the same current.

Question 24

A 100-W light bulb is connected to a 120-V DC power outlet.If the wires leading to that power outlet have a resistance of 1.2 ohms,how much power is wasted in the connecting wires?

A)0.83 W
B)1.0 W
C)1.2 W
D)1.4 W
E)99 W

Question 25

A 1-m copper wire with a radius of 0.5 mm is stretched to a distance of 2 m.What is the fractional change in resistance $\Delta$ R/R as the wire is stretched?

A)1.0
B)2.5
C)3.0
D)4.3
E)5.4

Question 26

Which of the following has the largest current flowing through it?

A)a 1-m long copper wire of diameter 1 mm connected to a battery of 10 V
B)a 0.5-m long copper wire of diameter 0.5 mm connected to a 5-V battery
C)a 2-m long copper wire of diameter 2 mm connected to a 20-V battery
D)a 1-m long copper wire of diameter 0.5 mm connected to a 5-V battery
E)All of the choices have the same current.

Question 27

A 10-ohm resistor is attached to a 20-ohm resistor in series.This combination is then attached to a 30-ohm resistor in parallel.This is then connected to a 120-V battery.What is the current flow through the 20-ohm resistor?

A)4.0 A
B)6.0 A
C)8.0 A
D)16 A
E)18 A

Question 28

A circuit consists of a copper wire of length 10 m and radius 1 mm.The wire is connected to a 10-V battery.An aluminum wire of length 5 m is connected to the same battery and dissipates the same amount of power.What is the radius of the aluminum wire?

A)0.91 mm
B)0.84 mm
C)1.12 mm
D)0.45 mm
E)0.65 mm

Question 29

After a long period of use,contacts in an electric bulb socket could corrode and introduce extra resistance in the circuit.Suppose a light bulb socket is very badly corroded and you are using a 100-W bulb in the corroded socket at 120 V.As a result,the actual power dissipated in the bulb is 80.0 W.What is the resistance of the badly corroded socket?

A)10 $\varOmega$
B)13 $\varOmega$
C)17 $\varOmega$
D)21 $\varOmega$
E)25 $\varOmega$

Question 30

Two identical bulbs,A and B,are connected in an electrical circuit as shown in the figure.R is the resistance connected in series with the each bulb.Initially they are glowing with equal intensity.Bulb A is removed from the socket;the potential difference across the empty socket A will

A)decrease.
B)increase.
C)not change.
D)become zero.

Question 31

A circuit consists of a copper wire of length 10 m and radius 1 mm.The wire is connected to a 10-V battery.An aluminum wire of radius 0.50 mm is connected to the same battery and dissipates the same amount of power.What is the length of the aluminum wire?

A)5.00 m
B)2.50 m
C)1.87 m
D)1.52 m
E)3.74 m

Question 32

In circuit shown,three identical light bulbs are connected.Initially switch S is closed.When switch S is opened,bulb 3 turns off.As for bulbs 1 and 2,which statement is true?

A)Bulb 1 gets brighter while bulb 2 gets dimmer.
B)Both bulbs 1 and 2 get brighter.
C)Both bulbs 1 and 2 get dimmer.
D)Bulb 1 gets dimmer while bulb 2 gets brighter.

Question 33

A current flows through an aluminum wire.The aluminum wire has a length of 2.00 m,a diameter of 0.0300 cm,and a carrier density of 6.02 * 10²⁸ electrons/m³.If the electron drift velocity is 1.84 * 10^-4 m/s,what is the current density in the wire?

A)1.93 * 10⁶ A/m²
B)1.18 * 10⁶ A/m²
C)1.36 * 10⁶ A/m²
D)1.53 * 10⁶ A/m²
E)1.77 * 10⁶ A/m²

Question 34

A 10-ohm resistor is attached to a 20-ohm resistor in series.This combination is then attached to a 30-ohm resistor in parallel.This is then connected to a 120-V battery.What is the current drawn from the battery?

A)2.0 A
B)2.2 A
C)3.3 A
D)8.0 A
E)1800 A

Question 35

After a long period of use,contacts in an electric bulb socket could corrode and introduce extra resistance in the circuit.Suppose a light bulb socket is very badly corroded and has 10 ohm of resistance.If you are using a 100-W bulb in the corroded socket at 120 V,the actual power dissipated in the bulb is

A)139.5 W.
B)112 W.
C)93.5 W.
D)87.4 W.
E)67.1 W.

Question 36

In an emergency you need to power a radio that uses 25 W of power when attached to a 6.0-V power supply.The only power supply you have access to provides 120 V,but you do have a very large number of 4.0-ohm resistors.If you want the power in the radio to be as closes as possible to 25 W,how many resistors do you need to use?

A)5
B)7
C)10
D)120
E)144

Question 37

Two resistors of resistance R are connected in series.The combination is connected in parallel to a resistor of resistance 2R.What is the resistance of this combination of resistors?

A)0.5 R
B)R
C)1.0 R
D)2.0 R
E)2.5 R

Question 38

A 12.0-V battery is connected to a 7.54-ohm resistor and a current of 0.999A is measured to flow through the resistor.How much power is dissipated as heat inside the battery?

A)zero
B)4.47 W
C)7.10 W
D)12.0 W
E)19.1 W

Question 39

Two resistors of resistance R are connected in parallel.The combination is connected in series to a resistor of resistance 2R.What is the resistance of this combination of resistors?

A)0.5 R
B)R
C)1.0 R
D)2.0 R
E)2.5 R

Question 40

A copper wire of diameter 2 mm carries 12 A of current for an electric stove.Assuming the resistivity of copper of 1.7 * 10^-8 $\varOmega$ .m,the power dissipated in 2 m length of the wire is

A)0.72 W.
B)0.98 W.
C)1.23 W.
D)1.44 W.
E)1.56 W.

Question 41

Assuming that there are 0.845 * 10²⁹ electrons per m³ in a wire with cross sectional area 69 mm² and drift velocity 4.12 * 10^-8 m/s,what is the density current in the wire?

A)557 A/m²
B)348 A/m²
C)300 A/m²
D)807 A/m²
E)652 A/m²

Question 42

Assuming that there are 0.845 * 10²⁹ electrons per m³ in a wire of with cross sectional area 69 mm² and carrying a current of 30 mA,what is the drift velocity?

A)3.21 * 10^-8 m/s
B)2.52 * 10^-5 m/s
C)8.22 * 10^-3 m/s
D)4.12 * 10⁶ m/s
E)3.00 * 10⁸ m/s

Question 43

A particular wire has a diameter of 1.7 mm and length of 1.3 m.If 45 $\mu$ V is the potential drop measured across the wire when 3.0 mA flow in it,what is the resistivity of the metal from which it is made?

A)1.0 * 10^-7 $\varOmega$ m
B)2.6 * 10^-8 $\varOmega$ m
C)4.4 *10^-6 $\varOmega$ m
D)1.8 * 10^-5 $\varOmega$ m

Question 44

A battery has an internal resistance of 1.3 $\varOmega$ and a voltage of 48 V.What is the load resistance which causes the voltage to drop to 45.4 V?

A)22.7
B)0.587
C)1.37
D)2.63
E)3.23

Question 45

Assuming that there are 0.845 * 10²⁹ electrons per m³ in a wire with cross sectional area 69 mm² and drift velocity 4.12 * 10^-8 m/s,what is the current in the wire?

A)25 mA
B)38 mA
C)33 mA
D)30 mA
E)18 mA

Question 46

A circuit containing a battery with V = 10.3 V and a resistor R1 = 15.7 $\varOmega$ is shown.If we replace the wire between points a and b with a second resistor R2 = 26.8 $\varOmega$ ,by how much (in a)will the total current through the battery change?

A)-0.265
B)-0.331
C)-0.414
D)-0.517
E)-0.646

Question 47

A particular wire has a diameter of 1.7 mm and length of 1.3 m.If its resistance is 15 m $\varOmega$ ,what is the resistivity of the metal from which it is made?

A)1.0 * 10^-7 $\varOmega$ m
B)2.6 * 10^-8 $\varOmega$ m
C)4.4 * 10^-6 $\varOmega$ m
D)1.8 * 10^-5 $\varOmega$ m

Question 48

A battery has an unloaded terminal voltage of 48 V.When a load of 15 $\varOmega$ is connected to the battery,the terminal voltage drops to 45.4 V.What is the internal resistance of the battery?

A)1.0 $\varOmega$
B)1.2 $\varOmega$
C)1.3 $\varOmega$
D)0.86 $\varOmega$
E)0.95 $\varOmega$

Question 49

In the circuit shown,R1 = 9.00 $\varOmega$ ,R2 = 14.0 $\varOmega$ ,R3 = 2.50 $\varOmega$ ,and V = 16.0 V.Find the total power dissipated in the circuit (in W).

A)10.53
B)15.26
C)22.13
D)32.09
E)46.53

Question 50

What is the current that flows out of the ideal 9-V battery in the circuit in the figure?

A)0.07 A
B)0.43 A
C)0.54 A
D)0.90 A
E)3.0 A

Question 51

What is the current in the 20 $\varOmega$ resistor in the circuit in the figure?

A)0.33 A
B)0.60 A
C)1.0 A
D)1.5 A
E)3.0 A

Question 52

Two cylinders are made out of the same material and are of equal length as shown.The cylinders are connected to a battery with voltage Vb as shown.If the voltage drop across resistor R2 is 0.810 * Vb,what is the ratio of the radii r1/r2 of the two cylinders?

A)1.10
B)1.29
C)1.51
D)1.76
E)2.06

Question 53

What is voltage across the 8 $\varOmega$ resistor?

A)4 V
B)8 V
C)12 V
D)1/4 V
E)1/8 V

Question 54

When two resistors are connected in parallel across a 12-V battery,6.3 A flows.If the smaller resistor is 2.5 $\varOmega$ how much current flows when the two are put in series across the same battery?

A)0.66 A
B)1.1 A
C)1.3 A
D)3.0 A
E)3.8 A

Question 55

Two conductors are made from the same material and are of the same length but one has a circular cross sectional area with diameter 1.2 mm and the other is square with 0.6 mm on each side.What is the ratio R_circular/R_square of their resistances?

A)R_circular/R_square = 2
B)R_circular/R_square = 1/ $\pi$
C)R_circular/R_square = $\pi$ /2
D)R_circular/R_square = 4
E)R_circular/R_square = 1/2

Question 56

A battery has an internal resistance of 1.3 $\varOmega$ and a voltage of 48.0 V.Is a load of 15.0 $\varOmega$ is connected to the battery,what is the voltage across the terminals of the battery?

A)48.0 V
B)44.2 V
C)45.4 V
D)39.6 V
E)42.0 V

Question 57

When two resistors are connected in series across a 12-V battery,1.1A flows.When they are connected in parallel across the same battery,6.3A flows.What is the smaller resistor's value?

A)2.5 $\varOmega$
B)8.4 $\varOmega$
C)1.7 $\varOmega$
D)0.55 $\varOmega$

Question 58

A battery has an internal resistance of 1.3 $\varOmega$ and a voltage of 48.0 V.Is a load of 15.0 $\varOmega$ is connected to the battery,what is the current supplied by the battery

A)2.94 A
B)37.0 A
C)2.63 A
D)3.20 A
E)2.48 A

Question 59

Two identical light bulbs are connected to a battery.Will the light bulbs be brighter if they are connected to the battery in series or in parallel?

A)in series
B)in parallel
C)The brightness will be the same in series and in parallel.
D)There is not enough information to determine an answer.

Question 60

A particular wire has a diameter of 1.7 mm and length of 1.3 m.If the resistivity of the metal from which the wire is made is 2.0 * 10^-8 $\varOmega$ m,and 45 $\mu$ V is the observed potential drop measured across the wire,what current is flowing in the wire?

A)3.9 mA
B)6.6 mA
C)16 mA
D)26 mA

Question 61

What is the current in the 5 $\varOmega$ resistor?

A)3.3 A
B)2.2 A
C)330 A
D)6.6 A
E)165 A

Question 62

A ribbon of nichrome (resistivity = 1.00 * 10^-6 $\varOmega$ ·m)with a rectangular cross sectional area and length 21.9 cm is used as a heating element in a toaster.What is the cross-sectional area of the ribbon,if the total resistance is intended to be 1.5 $\varOmega$ ?

A)1.24 mm²
B)1.02 mm²
C)0.79 mm²
D)0.25 mm²
E)0.33 mm²

Question 63

A ribbon of material with a rectangular cross sectional area of (0.25 mm * 1.00 mm),length 21.9 cm and resistance 1.5 $\varOmega$ is used as a heating element in a toaster.What is the resistivity of the material?

A)1.50 * 10^-6 $\varOmega$ ·m
B)1.71 * 10^-6 $\varOmega$ ·m
C)1.31 * 10^-6 $\varOmega$ ·m
D)1.97 * 10^-6 $\varOmega$ ·m
E)1.00 * 10^-6 $\varOmega$ ·m

Question 64

A wire of length L,diameter d,resistance R is made of material with resistivity $\rho$ .If I take the wire and cut it into five equal pieces and then put those pieces in parallel to make one single thick wire L/5 in length,what will be its resistance?

A)R/5
B)R/25
C)R
D)5R
E)25R

Question 65

Suppose,while cooling your bedroom 0.25 moles of electrons pass through your air conditioner each hour.What current does your air conditioner draw when it is running?

A)6.7 A
B)25 A
C)15 A
D)8.3 A
E)5.5 A

Question 66

In order to double the power dissipated in the resistor R,I should

A)double the resistance R.
B)double the voltage V.
C)increase the voltage V by about 40%.
D)decrease the resistance R by a factor of four.
E)decrease the voltage V by a factor of two.

Question 67

Suppose your air conditioner draws 5.5A while cooling your bedroom.How many moles of electrons pass through the air conditioner each hour the AC is on?

A)0.25
B)2.0
C)0.024
D)0.21
E)2.4 * 10^-7

Question 68

A ribbon of nichrome (resistivity = 1.00 * 10^-6 $\varOmega$ ·m)with a rectangular cross sectional area of (0.25 mm * 1.00 mm)will be used as a heating element in a toaster.How long should this ribbon be,if the total resistance is intended to be 1.5 $\varOmega$ ?

A)1.24 cm
B)2.79 cm
C)12.4 cm
D)21.9 cm
E)37.5 cm

Question 69

Assuming that the drift velocity in a wire of with cross sectional area 69 mm² is 4.12 * 10^-8 m/s and the current in the wire is current I = 30 mA,what is the density of electrons in the wire?

A)0.812 * 10²⁹ electrons per m³
B)0.845 * 10²⁹ electrons per m³
C)0.702 * 10²⁹ electrons per m³
D)0.756 * 10²⁹ electrons per m³
E)0.660 * 10²⁹ electrons per m³

Question 70

What is the current supplied by the battery?

A)9.9 A
B)6.6 A
C)3.3 A
D)2.2 A
E)165 A

Question 71

The resistivity of a metal at room temperature is 2.35 * 10^-8 $\varOmega$ *m.When the same metal is 150 ^$\circ$ C above room temperature,its resistivity is 4.55 * 10^-8 $\varOmega$ *m.What is the temperature coefficient for this metal?

A)5.38 * 10^-3/K.
B)3.98 * 10^-3/K.
C)2.64 * 10^-3/K.
D)6.24 *10^-3/K.
E)7.15 * 10^-3/K.

Question 72

Assuming there are 0.845 * 10²⁹ electrons per m³ and the drift velocity in a wire is 4.12 * 10^-8 m/s.If the current in the wire is 30 mA,what is the cross-sectional area of the wire?

A)50 mm²
B)69 mm²
C)63 mm²
D)45 mm²
E)54 mm²

Question 73

The resistivity of gold at room temperature is 2.35 * 10^-8 $\varOmega$ *m.The temperature coefficient $\alpha$ = 3.98 * 10^-3/K.What will be the resistivity of a piece of gold whose temperature is 150 ^$\circ$ C above room temperature?

A)2.35 * 10^-6 $\varOmega$ *m
B)4.55 * 10^-8 $\varOmega$ *m
C)0.95 * 10^-9 $\varOmega$ *m
D)2.35 * 10^-8 $\varOmega$ *m
E)3.75 * 10^-8 $\varOmega$ *m

Question 74

Which one of these circuits has the highest resistance between points A and B?

A)The left one has the highest resistance.
B)The middle one has the highest resistance.
C)The right one has the highest resistance.
D)All three have the same resistance.
E)The middle and right ones have the same resistance,and the left one's is lower.

Question 75

The current of 0.15 A flows through three resistors,R₁ = 20 Ohm,R₂ = 50 Ohm,R₃ = 65 Ohm,connected in series.What is the power dissipated in the R₂ resistor?

A)7.5 W
B)5.0 W
C)1.125 W
D)333 W
E)375 W

Question 76

What is the total power dissipated in both resistors?

A)0.68 W
B)5.2W
C)12.3 W
D)168 W
E)257 W

Question 77

A ribbon of nichrome (resistivity = 1.00 * 10^-6 $\varOmega$ ·m)with a rectangular cross sectional area of (0.25 mm * 1.00 mm)and 21.9 cm in length is used as a heating element in a toaster.What is the total resistance of this ribbon?

A)0.88 $\varOmega$
B)1.3 $\varOmega$
C)1.1 $\varOmega$
D)1.5 $\varOmega$
E)1.0 $\varOmega$

Question 78

A wire of radius R carries a current I.The current density is given by the function J = J₀ (1 - r/R)where r is measured from the center of the wire and J₀ is a constant.What is the value of J₀ if I = 1A,R = 1.5 mm (in A/m²)?

A)3.18 * 10^-1
B)4.76 * 10³
C)1.06 * 10⁵
D)4.24 * 10⁵
E)2.12 * 10⁵

Question 79

The resistivity of gold at room temperature is 2.35 * 10^-8 $\varOmega$ *m and its temperature coefficient is 3.98*10^-3/K.At what temperature will its resistivity equal 4.55 *10^-8 $\varOmega$ *m?

A)486 ^$\circ$ C above room temperature
B)130 ^$\circ$ C above room temperature
C)150 ^$\circ$ C above room temperature
D)425 ^$\circ$ C above room temperature
E)235 ^$\circ$ C above room temperature

Question 80

Consider this circuit.Let R₁ = R₂ = R₃ = R₄ = R₅ = 10 $\varOmega$ .If V= 20 V then what is the current I_V going through the circuit?

A)0.5 A
B)1.0 A
C)1.5 A
D)2.0 A
E)10.0 A