Free Printable Current Electricity

1.

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

a)

Drift velocity alone

b)

Thermal velocity alone

c)

Both A and B

d)

Neither A nor B

2.

13. Drift velocity vd varies with the intensity of electric field as per the relation

a)

(a) v_d ∝ E

b)

(b) v_d ∝ 1/E

c)

(c) v_d = constant

d)

(d) v_d ∝ E²

3.

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

4.

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

5.

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

6.

The conductance of a conductor of resistance 2 milli ohm

a)

5 Siemen

b)

0.5 Siemen

c)

50 Siemen

d)

500 Siemen

7.

The average relaxation time during collision of electrons with atoms is

a)

10^-14sec

b)

10^-10

c)

10⁴

d)

10¹⁴

8.

The dimensional formula of current density is

a)

⌈ L^-2 A ⌉

b)

⌈ L²A^-1⌉

c)

⌊ L^-1 A² ⌋

9.

n e V_{d = ____ ?}

a)

σ

b)

ρ

c)

j

d)

G

10.

Current density formula is

a)

Electric Current / length

b)

Electric Current / area

c)

Electric Current / volume

d)

None of above

11.

Directions of drift velocity of electrons and electric field are

a)

In same direction

b)

Opposite to each other

c)

Fluctuated

d)

None of above

12.

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

13.

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 $\times10^{23}$

14.

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

15.

There are 6.23 $\times10^{24}$ free electrons per $cm^3$ in a wire. The average drift velocity of the electrons is 1.1 $\times10^{-3}m\ s^{-1}$ . Calculate the current density in the wire.

a)

1.0 $\times10^3A\ m^{-2}$

b)

6.9 $\times10^6A\ m^{-2}$

c)

2.1 $\times10^9A\ m^{-2}$

d)

1.1 $\times10^9A\ m^{-2}$

16.

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

17.

A charge of 60 Coulomb flows in a wire for 45 minutes. If the diameter of the wire is 1.0 mm, what is the current density in the wire?

a)

2.2 $\times10^4A\ m^{-2}$

b)

2.8 $\times10^4A\ m^{-2}$

c)

7.6 $\times10^7A\ m^{-2}$

d)

5.6 $\times10^8A\ m^{-2}$

18.

The conductivity of copper is 6.0 $\times10^7\Omega^{-1}m^{-1}.$ The free electron density copper is 8.45 $\times10^{28}m^{-3}$ . Estimate the mean time between collisions of free electrons and positive ions in copper.

a)

2.52 $\times10^{-14}\ s$

b)

4.04 $\times10^{-33}\ s$

c)

4.04 $\times10^{-14}\ s$

d)

7.10 $\times10^{-22}\ s$

19.

The conductivity of copper is 6.0 $\times10^7\Omega^{-1}m^{-1}.$ The free electron density copper is 8.45 $\times10^{28}m^{-3}$ . Estimate the mean time between collisions of free electrons and positive ions in copper.

a)

2.52 $\times10^{-14}\ s$

b)

4.04 $\times10^{-33}\ s$

c)

4.04 $\times10^{-14}\ s$

d)

7.10 $\times10^{-22}\ s$

20.

A charge of 60 Coulomb flows in a wire for 45 minutes. If the diameter of the wire is 1.0 mm, what is the current density in the wire?

a)

2.2 $\times10^4A\ m^{-2}$

b)

2.8 $\times10^4A\ m^{-2}$

c)

7.6 $\times10^7A\ m^{-2}$

d)

5.6 $\times10^8A\ m^{-2}$

Current Electricity - Drift velocity

Total questions: 20

Worksheet time: 5hrs 0mins

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