# Physics

1. The current passing through a room heater has been halved. What will happen to the heat produced by it?

2. An electric iron of resistance 20 ohm draws a current of 5 amperes. Calculate the heat produced in 30 seconds.

3. An electric heater of resistance 8 ohm takes a current of 15 A from the mains supply line. Calculate the rate at which heat is developed in the heater.

4. A resistance of 40 ohms and one of 60 ohms are arranged in series across 220 volt supply. Find the heat in joules produced by this combination in half a minute.

5. A resistance of 25 ohm is connected to a 12 V battery. Calculate the heat energy in joules generated per minute.

6. 100 joules of heat is produced per second in a 4 ohm resistor. What is the potential difference across the resistor?

7. An electric iron is connected to the mains power supply of 220 V. When the electric iron is adjusted at minimum heating’ it consumes a power of 360 W but at ‘maximum heating’ it takes a power of 840 W. Calculate the current and resistance in each case.

8. Ten bulbs are connected in a series circuit to a power supply line. Ten identical bulbs are connected in a parallel circuit to an identical power supply line.
1. Which circuit would have the highest voltage across each bulb
2. In which circuit would the bulbs be brighter?
3. In which circuit, if one bulb blows out, all others will stop glowing?
4. Which circuit would have less current in it?

9. Calculate the cost of operating a heater of 500 W for 20 hours at the rate of Rs. 3.90 per unit.

10. Which has a greater resistance, a 100 watt bulb or a 60 watt bulb?

11. How much energy is consumed when a current of 5 amperes flows through the filament (or element) of a heater having resistance of 100 ohms for two hours? Express it in joules.

12. An electric bulb is rated at 220 V, 100 W. What is its resistance?

13. An electric bulb is connected to a 220 V power supply line. If the bulb draws a current...