Question

An electric heater takes 1.2kwh in 30min at 120V having an efficiency of 99%.The heat energy required boil a certain amount of water is 99KJ.If the current taken by heater is 20 amp at 120V.Find the time required to boil water?

Answer 1

The time required to boil the water is 30 minutes.

Step-by-step explanation:

To find the time required to boil water, we need to calculate the power of the electric heater first. Power is the rate at which energy is consumed. We can calculate it using the formula:

Power (P) = Current (I) x Voltage (V)

Given that the current is 20 amps and the voltage is 120 volts, we can substitute these values into the formula to find the power:

P = 20 amps x 120 volts = 2400 watts

Next, we need to convert the energy consumed by the heater to kilowatt-hours (kWh). The formula to do this is:

Energy (E in kWh) = Power (P in watts) x Time (T in hours) / 1000

Given that the energy consumed is 1.2 kWh and the power is 2400 watts, we can rearrange the formula to solve for time:

T = (Energy x 1000) / Power = (1.2 kWh x 1000) / 2400 watts = 0.5 hours = 30 minutes

Therefore, it would take 30 minutes to boil the water.

Answer 2

Step-by-step explanation:

Power of the heater = P watt .

P x .5 = 1200

P = 2400 W

If resistance of heater R

V² / R = 2400

120²/ R = 2400

R = 6 ohm .

heat to be produced = 99000 J

Current be I

I²R t x .99 = 99000

20² x 6 x t x .99 = 99000

t = 41.67 s