CAIE IGCSE Physics Electrical Energy and Power Questions

Practise calculating electrical power and energy, converting time and units, interpreting kilowatt-hours and connecting circuit values with appliance operation.

Exam points

use P = IV and E = Pt = IVt to calculate power, transferred energy, current or operating time
convert minutes to seconds for joules or watts and use hours with kilowatts for energy in kWh
combine efficiency or resistance steps with appliance ratings before calculating useful energy

Covered syllabus points

4.2.5.1—Electric circuits transfer energy from 4.2.5.2—Recall/use: for electrical power P =4.2.5.3—Recall/use: for electrical energy E =4.2.5.4—Kilowatt-hour (kWh) and calculate the

[Maximum number: 4]

(a)

Fig. 6.2 shows a circuit containing two resistors, P and Q . The circuit is powered by a 12 V battery.

Fig. 6.2

[ 4 ]

(i)

Calculate the energy transferred electrically when the current calculated in (b)(i) is present in resistor Q for 5 minutes.

energy =

[ 3 ]

610 J OR 620 J

A3

$E=I \times V \times t \boldsymbol{OR}$ ( E= ) $V \times I \times t \boldsymbol{OR}$ ( E= ) $12 \times 0.17 \times 300$

C1

$300(\mathrm{~s})$ OR $5 \times 60$

C1

(ii)

Energy is transferred from the battery by the electrical current.

State the energy store in the battery.

[ 1 ]

[Maximum number: 2]

Fig. 3.1 shows a model of a wind turbine used to demonstrate the use of wind energy to generate electricity. The wind is blowing towards the model, as shown.

Fig. 3.1

The output current of the generator is 2.0 A . The output potential difference (p.d.) of the generator is 11 V .

Calculate the output power of the generator.

output power =

P=VI in any form OR $11 \times 2$

C1

22 W

A1

[Maximum number: 2]

Fig. 9.1 shows a 12 V battery connected in a circuit containing resistors A, B, C and D. Each resistor has a resistance of $6.0 \Omega$ .

Fig. 9.1

Calculate

the energy transferred from the battery to the circuit in 50 s .
energy transferred =

$\begin{aligned} (E=) \text { IVt OR } 1.2 \times 12 \times 50 \text { OR } I^{2} \text { Rt OR } 1.2^{2} \times 10 \times 50 \text { OR } V^{2} t / \text { R OR } 12^{2} \times 50 / 10 720 \mathrm{~J} \end{aligned}$
C1
A1
Total: 7

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Covered syllabus points

4.2.5 Electrical energy and electrical power question 1

Question (a)

Question (i)

Question (ii)

4.2.5 Electrical energy and electrical power question 2

4.2.5 Electrical energy and electrical power question 3