Page 202 - WCS - Electrical

WORKSHOP CALCULATION & SCIENCE - CITS

Voltage drop = 12V – 10.8 = 1.2V

The supply voltage is called Potential difference.
Example

The Internal resistance of a dynamo is 0.1 ohm. The voltage of dynamo is 12V. What is the Voltage of dynamo
when a current of 20 amps being supplied to an outside circuit.
Solution
Voltage drop = Current x Internal resistance

= 20 x 0.1 volts
= 2 volts
Example (Fig 6)
The Internal resistance of a Battery is 2 ohms. When a resistance of 10 ohms is connected to a battery it draws
0.6 amps. What is the EMF of the battery.
P.D = Current flowing x Resistance
= 0.6 A x 10W

= 6 volts
V.D = Current flowing x Internal resistance of battery
= 0.6 x 2 volts
= 1.2 volts
EMF of the Battery = (6.00 + 1.2)V
= 7.2 volts

189

CITS : WCS - Electrical - Exercise 18