Question 1

A current of 0.3 A passes through a lamp for 2 minutes using a 6 V power supply. The energy dissipated by this lamp during the 2 minutes is:

Accepted Answer

A)  1.8 J 
B)  12 J 
C)  20 J 
D)  36 J 
E)  216 J 
A)  1.8 J 
B)  12 J 
C)  20 J 
D)  36 J 
E)  216 J

Question 2

Conductivity is:

Accepted Answer

A)  the same as resistivity, it is just more convenient to use for good conductors 
B)  expressed in  $\Omega$ -1 
C)  equal to 1/resistance 
D)  expressed in ( $\Omega$ .m)-1  
E)  not a meaningful quantity for an insulator 
A)  the same as resistivity, it is just more convenient to use for good conductors 
B)  expressed in  $\Omega$ -1 
C)  equal to 1/resistance 
D)  expressed in ( $\Omega$ .m)-1  
E)  not a meaningful quantity for an insulator

Question 3

Five cylindrical wires are made of the same material. Their lengths and radii are   Rank the wires according to their resistances, least to greatest.

Accepted Answer

A)  1, 2, 3, 4, 5 
B)  5, 4, 3, 2, 1 
C)  1 and 2 tie, then 5, 3, 4 
D)  1, 3, 4, 2, 5 
E)  1, 2, 4, 3, 5 
A)  1, 2, 3, 4, 5 
B)  5, 4, 3, 2, 1 
C)  1 and 2 tie, then 5, 3, 4 
D)  1, 3, 4, 2, 5 
E)  1, 2, 4, 3, 5

Question 4

For an ohmic substance, the electron drift velocity is proportional to:

Accepted Answer

A)  the cross-sectional area of the sample 
B)  the length of the sample 
C)  the mass of an electron 
D)  the electric field in the sample 
E)  none of the above 
A)  the cross-sectional area of the sample 
B)  the length of the sample 
C)  the mass of an electron 
D)  the electric field in the sample 
E)  none of the above

Question 5

A certain x-ray tube requires a current of 7 mA at a voltage of 80 kV. The rate of energy dissipation is:

Accepted Answer

A)  5600 W 
B)  560 W 
C)  26 W 
D)  11.4 W 
E)  0.088 W 
A)  5600 W 
B)  560 W 
C)  26 W 
D)  11.4 W 
E)  0.088 W

Question 6

The resistance of a rod does NOT depend on:

Accepted Answer

A)  its temperature 
B)  its material 
C)  its length 
D)  its conductivity 
E)  shape of its (fixed) cross-sectional area 
A)  its temperature 
B)  its material 
C)  its length 
D)  its conductivity 
E)  shape of its (fixed) cross-sectional area

Question 7

In schematic diagrams, currents are indicated using arrows. What do the arrows indicate?

Accepted Answer

A)  the direction of motion of the electrons 
B)  the direction of the current vector 
C)  the direction of motion of the charge carriers 
D)  the direction that positive charge carriers would move 
E)  nothing; they are just a convenient drawing tool 
A)  the direction of motion of the electrons 
B)  the direction of the current vector 
C)  the direction of motion of the charge carriers 
D)  the direction that positive charge carriers would move 
E)  nothing; they are just a convenient drawing tool

Question 8

Suppose the electric company charges 10 cents per kW.h. How much does it cost to use a 125 watt lamp 4 hours a day for 30 days?

Accepted Answer

A)  $1.20 
B)  $1.50 
C)  $1.80 
D)  $7.20 
E)  none of these 
A)  $1.20 
B)  $1.50 
C)  $1.80 
D)  $7.20 
E)  none of these

Question 9

The current is zero in a conductor when no potential difference is applied because:

Accepted Answer

A)  the electrons are not moving 
B)  the electrons are not moving fast enough 
C)  for every electron with a given velocity there is another with a velocity of equal magnitude and opposite direction 
D)  equal numbers of electrons and protons are moving together 
E)  otherwise Ohm's law would not be valid 
A)  the electrons are not moving 
B)  the electrons are not moving fast enough 
C)  for every electron with a given velocity there is another with a velocity of equal magnitude and opposite direction 
D)  equal numbers of electrons and protons are moving together 
E)  otherwise Ohm's law would not be valid

Question 10

Which of the following graphs best represents the current-voltage relationship of an incandescent light bulb?

Accepted Answer

A)  I 
B)  II 
C)  III 
D)  IV 
E)  V 
A)  I 
B)  II 
C)  III 
D)  IV 
E)  V

Question 11

A 10-ohm resistor has a constant current. If 1200 C of charge flow through it in 4 minutes what is the value of the current?

Accepted Answer

A)  3.0 A 
B)  5.0 A 
C)  20 A 
D)  120 A 
E)  300 A 
A)  3.0 A 
B)  5.0 A 
C)  20 A 
D)  120 A 
E)  300 A

Question 12

Current is a measure of:

Accepted Answer

A)  force that moves a charge past a point 
B)  resistance to the movement of a charge past a point 
C)  energy used to move a charge past a point 
D)  amount of charge that moves past a point per unit time 
E)  speed with which a charge moves past a point 
A)  force that moves a charge past a point 
B)  resistance to the movement of a charge past a point 
C)  energy used to move a charge past a point 
D)  amount of charge that moves past a point per unit time 
E)  speed with which a charge moves past a point

Question 13

The mechanical equivalent of heat is 1 cal = 4.18 J. A heating coil, connected to a 120-V source, develops 60,000 calories in 10 minutes. The current in the coil is:

Accepted Answer

A)  0.83 A 
B)  2.0 A 
C)  3.5 A 
D)  500 A 
E)  2100 A 
A)  0.83 A 
B)  2.0 A 
C)  3.5 A 
D)  500 A 
E)  2100 A

Question 14

Current has units:

Accepted Answer

A)  kilowatt·hour 
B)  coulomb/second 
C)  coulomb 
D)  volt 
E)  ohm 
A)  kilowatt·hour 
B)  coulomb/second 
C)  coulomb 
D)  volt 
E)  ohm

Question 15

An incandescent light bulb is marked "60 watt, 120 volt". Its resistance is:

Accepted Answer

A)  0.5 $\Omega$ 
B)  120  $\Omega$ 
C)  180  $\Omega$ 
D)  240  $\Omega$ 
E)  300  $\Omega$ 
A)  0.5 $\Omega$ 
B)  120  $\Omega$ 
C)  180  $\Omega$ 
D)  240  $\Omega$ 
E)  300  $\Omega$

Exam 26: Current and Resistance

A current of 0.3 A passes through a lamp for 2 minutes using a 6 V power supply. The energy dissipated by this lamp during the 2 minutes is:

Conductivity is:

Five cylindrical wires are made of the same material. Their lengths and radii are Rank the wires according to their resistances, least to greatest.

For an ohmic substance, the electron drift velocity is proportional to:

A certain x-ray tube requires a current of 7 mA at a voltage of 80 kV. The rate of energy dissipation is:

The resistance of a rod does NOT depend on:

In schematic diagrams, currents are indicated using arrows. What do the arrows indicate?

Suppose the electric company charges 10 cents per kW.h. How much does it cost to use a 125 watt lamp 4 hours a day for 30 days?

The current is zero in a conductor when no potential difference is applied because:

Which of the following graphs best represents the current-voltage relationship of an incandescent light bulb?

A 10-ohm resistor has a constant current. If 1200 C of charge flow through it in 4 minutes what is the value of the current?

Current is a measure of:

The mechanical equivalent of heat is 1 cal = 4.18 J. A heating coil, connected to a 120-V source, develops 60,000 calories in 10 minutes. The current in the coil is:

Current has units:

An incandescent light bulb is marked "60 watt, 120 volt". Its resistance is:

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