Question 1

For an ohmic resistor, resistance is the proportionality constant for:

Accepted Answer

A)  potential difference and electric field 
B)  current and electric field 
C)  current and length 
D)  current and cross-sectional area 
E)  current and potential difference 
A)  potential difference and electric field 
B)  current and electric field 
C)  current and length 
D)  current and cross-sectional area 
E)  current and potential difference E

Question 2

A certain wire has resistance R. Another wire, of the same material, has half the length and half the diameter of the first wire. The resistance of the second wire is:

Accepted Answer

A)  R/4 
B)  R/2 
C)  R 
D)  2R 
E)  4R 
A)  R/4 
B)  R/2 
C)  R 
D)  2R 
E)  4R D

Question 3

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 E

Question 4

If   is the current density and   is a vector element of area then the integral   over an area represents:

Accepted Answer

A)  the electric flux through the area 
B)  the average current density at the position of the area 
C)  the resistance of the area 
D)  the resistivity of the area 
E)  the current through the area 
A)  the electric flux through the area 
B)  the average current density at the position of the area 
C)  the resistance of the area 
D)  the resistivity of the area 
E)  the current through the area

Question 5

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

Accepted Answer

A)  560 
B)  5600 
C)  26 
D)  11.4 
E)  87.5 
A)  560 
B)  5600 
C)  26 
D)  11.4 
E)  87.5

Question 6

A 60-watt light bulb carries a current of 0.5 ampere. The total charge passing through it in one hour is:

Accepted Answer

A)  120 C 
B)  3600 C 
C)  3000 C 
D)  2400 C 
E)  1800 C 
A)  120 C 
B)  3600 C 
C)  3000 C 
D)  2400 C 
E)  1800 C

Question 7

A current of 0.5 ampere exists in a 60-ohm lamp. The applied potential difference is:

Accepted Answer

A)  15 V 
B)  30 V 
C)  60 V 
D)  120 V 
E)  none of these 
A)  15 V 
B)  30 V 
C)  60 V 
D)  120 V 
E)  none of these

Question 8

An certain resistor dissipates 0.5 W when connected to a 3 V potential difference. When connected to a 1 V potential difference, this resistor will dissipate:

Accepted Answer

A)  0.5 W 
B)  0.167 W 
C)  1.5 W 
D)  0.056 W 
E)  none of these 
A)  0.5 W 
B)  0.167 W 
C)  1.5 W 
D)  0.056 W 
E)  none of these

Question 9

For a cylindrical resistor made of ohmic material, the resistance does NOT depend on:

Accepted Answer

A)  the current 
B)  the length 
C)  the cross-sectional area 
D)  the resistivity 
E)  the electron drift velocity 
A)  the current 
B)  the length 
C)  the cross-sectional area 
D)  the resistivity 
E)  the electron drift velocity

Question 10

A current of 0.3 A is passed 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 11

If the potential difference across a resistor is doubled:

Accepted Answer

A)  only the current is doubled 
B)  only the current is halved 
C)  only the resistance is doubled 
D)  only the resistance is halved 
E)  both the current and resistance are doubled 
A)  only the current is doubled 
B)  only the current is halved 
C)  only the resistance is doubled 
D)  only the resistance is halved 
E)  both the current and resistance are doubled

Question 12

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 13

A cylindrical copper rod has resistance R. It is reformed to twice its original length with no change of volume. Its new resistance is:

Accepted Answer

A)  R 
B)  2R 
C)  4R 
D)  8R 
E)  R/2 
A)  R 
B)  2R 
C)  4R 
D)  8R 
E)  R/2

Question 14

Of the following the copper conductor that has the least resistance is:

Accepted Answer

A)  thin, long and hot 
B)  thick, short and cool 
C)  thick, long and hot 
D)  thin, short and cool 
E)  thin, short and hot 
A)  thin, long and hot 
B)  thick, short and cool 
C)  thick, long and hot 
D)  thin, short and cool 
E)  thin, short and hot

Question 15

For an ohmic substance, the resistivity depends on:

Accepted Answer

A)  the electric field 
B)  the potential difference 
C)  the current density 
D)  the electron mean free time 
E)  the cross-sectionalarea of the sample 
A)  the electric field 
B)  the potential difference 
C)  the current density 
D)  the electron mean free time 
E)  the cross-sectionalarea of the sample

Question 16

Five cylindrical wires are made of the same material.Their lengths and radii are
Wire 1: length   radius r
Wire 2: lenth   radius r/2
Wire 3: length   radius r/2
Wire 4: length   radius r/2
Wire 5: length   radius r/2
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

Exam 10: Current and Resistance

For an ohmic resistor, resistance is the proportionality constant for:

A certain wire has resistance R. Another wire, of the same material, has half the length and half the diameter of the first wire. The resistance of the second wire is:

The resistance of a rod does NOT depend on:

If is the current density and is a vector element of area then the integral over an area represents:

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

A 60-watt light bulb carries a current of 0.5 ampere. The total charge passing through it in one hour is:

A current of 0.5 ampere exists in a 60-ohm lamp. The applied potential difference is:

An certain resistor dissipates 0.5 W when connected to a 3 V potential difference. When connected to a 1 V potential difference, this resistor will dissipate:

For a cylindrical resistor made of ohmic material, the resistance does NOT depend on:

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

If the potential difference across a resistor is doubled:

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

A cylindrical copper rod has resistance R. It is reformed to twice its original length with no change of volume. Its new resistance is:

Of the following the copper conductor that has the least resistance is:

For an ohmic substance, the resistivity depends on:

Five cylindrical wires are made of the same material.Their lengths and radii are Wire 1: length radius r Wire 2: lenth radius r/2 Wire 3: length radius r/2 Wire 4: length radius r/2 Wire 5: length radius r/2 Rank the wires according to their resistances, least to greatest.

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