Please Answer as soon as possible 1. How much energy is transformed by an electric lamp in 100 s if a current of 0.22 A flows through it when it is connected to a 120 V supply?

2. A 10 V power supply pushes a current of 5.0 A through a resistor. At what rate is energy transferred to the resistor?

3. A tropical fish tank is fitted with an electric heater, which has a power rating of 30 W. The heater is connected to a 12 V supply. What current flows through the heater when it is switched on?

1. 2.64 kJ 2. 50 W 3. 2.5 A

Explanation:

1. Energy transformed in the lamp, E = IVt where I = current = 0.22 A, V = voltage = 120 V and t = time = 100s

E = 0.22 A × 120 V × 100 s

= 2640 J

= 2.64 kJ

2. The rate at which energy is trans ferred to the resistor is the power.

Power, P = IV where I = current = 5.0 A and V = voltage = 10 V

P = 5.0 A × 10 V = 50 W

3. Since Power P = IV

Current through the heater I = P/V P = 30 W and V = 12 V

I = 30 W/12 V

= 2.5 A

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