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1.

Which of the following characteristics of electrons determines the current in a conductor?

a)

A. Drift velocity alone

b)

B. Thermal velocity alone

c)

C. Both A and B

d)

D. Neither A nor B

2.

In the equation I = nAvq, what does v represent?

a)

The speed of the electrons

b)

The average speed of the electrons

c)

The velocity of the electrons

d)

The average velocity of the electrons

e)

the fastest speed of all electrons

3.

If the current in a specific copper wire increases this can be due to _____________________.

a)

An increase in the charge carrier density

b)

An increase in the electron drift speed

c)

An increase in its cross sectional area

d)

An increase in the charge of electrons

4.

If the current at a given point in a circuit is 2.5 Amp, then how many electrons pass that point on the circuit in a time period of 1 minute.

Answer:

a)

9.375 x 10²⁰ electrons

b)

9.375 x 10²¹ electrons

c)

9.375 x 10¹⁹ electrons

d)

9.375 x 10¹⁸ electrons

5.

A conductor of cross-sectional area 0.10 $mm^2$ carries a current of 2.5 A. If the number of conduction electrons per cubic metre is $1.0\times10^{28\ }$ $m^{-3}$ . What is the value of drift velocity of the free electrons in the conductor?

a)

1.6 $\times10^{-2}\ m\ s^{-1}$

b)

3.9 $\times10^{-2}\ m\ s^{-1}$

c)

3.0 $\times10^{-3\ }m\ s^{-1}$

d)

6.2 $\times10^{-3\ }m\ s^{-1}$

6.

A conductor of length 2.0 m and cross-sectional area 5.0 $\times10^{-6}\ m^2$ carries a current of 6.0 A. If the drift velocity of the conduction electrons is 1.5 $\times10^{-4}\ m\ s^{-1}$ , what is the number of electrons in the conductor?

a)

2.5 $\times10^{23}$

b)

2.9 $\times10^{23}$

c)

4.2 $\times10^{23}$

d)

5.0 $\times10^{23}$

7.

A tungsten wire of length 1.00 m and cross-sectional area 2.01 $\times10^{-6}\ m^2$ carries a current of 5.00 A. If the number of free electrons per unit volume is 4.3 $\times10^{28}$ , what is the time taken by an electron to travel from one end of the wire to the other end?

a)

1.81 $\times10^3$ s

b)

2.77 $\times10^3$ s

c)

4.51 $\times10^3$ s

d)

7.25 $\times10^3$ s

8.

A current flows in a copper wire. The current density in the wire is 1.4 $\times10^6A\ m^{-2}$ . If the number of free electrons in 1 $m^3$ of wire is 8.4 $\times10^{28}$ , what is the drift velocity of the electrons?

a)

1.04 $\times10^{-4}m\ s^{-1}$

b)

3.10 $\times10^{-4}m\ s^{-1}$

c)

1.67 $\times10^{-3}m\ s^{-1}$

d)

1.90 $\times10^{-3}m\ s^{-1}$

9.

In the equation I=nAvq, which option(s) describe the meaning of n?

a)

the charge carrier density

b)

the number of charge carriers per unit volume

c)

the number of charge carriers per m³

d)

the number of charge carriers in the wires

e)

the total charge carriers available in the battery

10.

When a thick wire is connected in series with a thin wire of the same material which of the below is/are true?

a)

The current through the thick wire is greater than the current through the thin wire

b)

The electrons move slower through the thin wire than through the thick wire

c)

The number of charge carriers per unit volume is greater in the thick wire than in the thin wire

d)

The number of charges flowing per second past a cross section of the thick wire is the same as that flowing past a cross section of the thin wire

11.

When a semiconducting and metallic wire of the same diameter are connected in series which of the below is/are true?

a)

The current in the semiconductor is greater than that in the metal

b)

The electrons move faster in the semiconductor

c)

The semiconductor has a lower value of n

d)

Each charge carrier in the semiconductor carries more charge than the charge carriers in the metal

12.

If the current in a conductor were to remain the same, what effect will doubling the charge carrier density have?

a)

Double the charge per charge carrier in the material

b)

Halve the average drift speed of the electrons

c)

Halve the cross sectional area of the wire

Science

Total questions: 12

Worksheet time: 36mins

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