Power Delivered and Heat Dissipated in a Circuit

Q. A constant voltage is applied between the two ends of a metallic wire. Some heat is developed in it. The heat developed is doubled if

1. both the length and the radius of the wire are halved
2. both the length and the radius of the wire are doubled
3. the length of the wire is doubled
4. the radius of the wire is halved

Q. An electric bell has a rating of 500 W 100 V. It is used in a circuit having a 200 V supply. What resistance must be connected in series with the bulb so that it delivers 500 W?

1. 10 ohm
2. 20 ohm
3. 30 ohm
4. 40 ohm

Q. An electric kettle has two coils. When one coil is connected to the AC mains the water in the kettle boils in 10 minutes. When the other coil is used the same quantity of water takes 15 minutes to boil. How long will it take for the same quantity of water to boil if the two coils are connected in parallel?

1. 24 min
2. 6 min
3. 12 min
4. 18 min

Q. A resistor of resistance R is connected to an ideal battery (battery with zero internal resistance). If the value of R is increased, the heat developed in the resistor for equal interval of time will ___.

1. increase
2. remains unchanged
3. Data insufficient
4. decrease

Q. What is the power in the given circuit?

1. 3.6 W
2. 35 W
3. 175W
4. 245W

Q. In the meter bridge experiment shown in figure, the balance length AC corresponding to null deflection of the galvanometer is x. What would be the balance length if the radius of the wire AB is doubled?

1. x
2. 4x
3. 2x
4. 

Q. A resistor of resistance R is connected to an ideal battery (battery with zero internal resistance). If the value of R is increased, the power dissipated in the resistor will___?

1. decrease
2. remains unchanged
3. Data insufficient
4. increase

Q. A resistor develops 1600 J of thermal energy in 50 s when a current of 2 A flows through it. If the current is increased to 10 A, what will be the thermal energy developed in the same amount of time?

1. 16 KJ
2. 80 KJ
3. 64 KJ
4. 40 KJ

Q. A battery of internal resistance $4\Omega$ is connected to the network of resistances as shown. In order to give the maximum power to the network, the value of $R\left(in\Omega \right)$ should be

1. 18
2. 4/9
3. 2
4. 8/9

Q. The voltage across a bulb is decreased by $2\%.$ Assuming that the resistance of the filament remains unchanged the power of the bulb will

1. increase by 2%
2. decrease by 4%
3. increase by 4%
4. decrease by 2%