Electricity Test - 8

A stream of electrons moving through a conductor constitutes an Electric current.

The Direction of electric current is opposite to the direction of flow electrons.

The Ohm’s law states that “The potential difference across the ends of a resistor is directly proportional to the current through it, provided its temperature remains the same”.

The resistance of the conductor depends upon

1) The resistivity of the material of the conductor.

2) The length of the conductor

3) The area of cross-section of the conductor

Nichrome is an alloy of Nickel, Chromium, manganese and iron. The alloy does not oxidise readily at high temperature.

Thus, Nichrome is used as heating element in electric toaster.

The resistance of the bulb is 1200Ω

The voltage applied by the source is 220V

Applying the ohm’s, we get

Voltage, V=IR

Where

I is the current

R is the resistance

Putting the values in the above formula, we get

220 V= 1200Ω × I

Solving For I, we get

I=0.18 A

Given:

The resistance of the electric heater, R= 200Ω

The current in the circuit, I =2A

Time period, t = 30 sec

Formula used:

Heat transferred, H= I² RT

Where

I is the current

R is the resistance

T is the time period

Putting the values in the above equation, we get

H= 2² × 200× 30 sec=24,000 J= 24 KJ

The commercial unit of electrical energy is kilowatt hour (kWH)

1 kWh=3,600,000 J=3.6 × 10⁶ J