Question

A student uses an electric heater to investigate efficiency. He places the heater in the aluminium block switches the heater on and measures the temperature of the block each minute for 20 minutes. The student wants to calculate the electrical energy supplied to the heater. a. Complete the table by recording the readings shown on the meters below. b. Show that the energy supplied to the heater in 20 minutes is about 30 000 J.

Answer 1

Explanation:

a ) Current in Amps = 2 A

    Voltage in Volts = 12.5 V

b) Now, Power = V*I = (12.5* 2) watt = 25 watt

so, energy supplied per second = 25 J

energy supplied in 20 minutes = (25 *20* 60 ) J     (1 minute= 60 second)

                                                    = 30,000 J

Answer 2

The energy supplied to the heater is 25 joules and the energy supplied to the heater in 20 minutes is 30,000 joules.

Given,

A figure shows the readings of the ammeter and voltmeter.

To Find,

The electrical energy supplied to the heater and the energy supplied to the heater in 20 minutes.

Solution,

In the given figure,

The reading of the ammeter is 2 amperes.

The reading of the voltmeter is 12.5 volts.

Now, the formula for calculating the power is

Power = V*I, where v is the voltage and i is the current.

Power = 2*12.5 = 25 watts.

So, the energy supplied to the heater per second = 25 joules.

Now,

The energy supplied in 20 minutes = 25*20*60 { 20 minutes = 20*60 seconds}

So,

Energy supplied = 30,000 joules.

Hence, the energy supplied to the heater is 25 joules and the energy supplied to the heater in 20 minutes is 30,000 joules.

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