Electricity Worksheet3

A conductor carries a current of 0.2 A. Find the amount of charge that will pass through the crosssection of the conductor in 30 s. How many electrons will flow in this time interval if the charge on one electron is 1.6 × 10^{–19} C ?

The filament of an electric lamp draws a current of 0.4 A which lights for 3 hours. Calculate the amount of charge that flows through the circuit.

An electric iron draws a current of 0.5 A when voltage is 200 V. Calculate the amount of charge flowing through it in one hour.

N electrons flow through a crosssection of a conductor in time t. if the charge on an electron is e, write an expression for the current in the conductor.

0.5 C charge passes through a crosssection of a conductor in 5 s. Find the current.

A polythene piece rubbed with wool is found to have negative charge of 3 × 10^{–7} C. Estimate the number of electrons transferred.

Calculate the current in a wire if 1500 C charge is passed through it in 5 minutes.

A current of 0.5 A is drawn by a filament of an electric bulb for 10 minutes. Find the amount of electric charge that flows through the electric circuit.

Calculate the amount of work done to carry 4C of charge from a point at 100 V to a point at 120 V.

What is the resistance of an electric arc lamp when hot, if the lamp uses 20 A when connected to a 220 volt line?
Answer:

Current I = 0.2A and time, t = 30 s
∴ charge, Q = I × t = 0.2 × 30 = 6 C
If n electrons flow and e is the charge on an electron, then
Q = ne so

current, I = 0.4 A and time t = 3 hours = 3 × 60 × 60 = 10800s
∴ charge, Q = I × t = 0.4 × 10800 = 4320 C

current I = 0.5 A and time, t = 1 hour = 60 × 60s = 3600 s
∴ charge, Q = I × t = 3600 × 0.5 = 1800 C



As Q = ne,


Q = It = 0.5 A × (10 × 60)s = 300 C

Potential difference between two points, V = 120 V – 100 V = 20 V
Charge to be moved, Q = 4 C
If W is the amount of work done, then
W = Q × V = 4 × 20 = 80 J

Potential difference across the arc lamp, V = 220 V
Current through the lamp, I = 20 A
∴ resistance of the lamp,