NUMERICALS
Electricity & its effects
11. A 2 Volt cell is connected to a 1 Ω resistor. How many electrons come out of the negative terminal of the cell in 2 minutes ?
12. a) How much current will an electric bulb draw from a 220 V source, if the resistance of the bulb filament is 1200 Ω ?
b) How much current will an electric heater coil draw from a 220 V source, if the resistance of the heater coil is 100 Ω ?
13. The potential difference between the terminals of an electric heater is 60 Volts when it draws a current of 4 Ampere from a source. What current will the heater draw if the potential difference is increased to 120 Volt.
14. A torch bulb when cold has 1Ω resistance. It draws a current of 0.3 Ampere when glowing from a source of 3 V. Calculate the resistance of the bulb when glowing and explain the reason for the difference in resistance.
15. A current of 0.2 Ampere flows through a conductor of resistance 4.5 Ω. Calculate the potential difference at the ends of the conductor.
16. A resistance of 6 ohms is connected in series with another resistance of 4 ohms. A potential difference of 20 volts is applied across the combination. Calculate the current through the circuit and potential difference across the 6 ohm resistance.
17. Resistors R1, R2, R3 having values 5Ω, 10 Ω, 30 Ω respectively are connected in parallel across a battery of 12 Volts. Calculate
(i) Current through each resistor .
(ii) Total current.
(iii) Total resistance.
18. In the circuit diagram below, find
(i) total resistance of the circuit
(ii) total current flowing in the circuit .
(iii) potential difference across R1. [C.B.S.E. 1990, 1993]
19. An electric lamp of 100 Ω, a toaster of resistance 50 Ω , and a water filter of resistance 500 Ω are connected in parallel to a 220 Volt source. What is the resistance of an electric iron connected to the same source that takes as much current as all three appliances, and what is the current through it ?
20. How can three resistances of 2Ω, 3Ω & 6Ω be connected to give the total resistance of
a) 4Ω b) 1 Ω
