CAIE IGCSE Physics 1.7.4 Power Questions

Covered syllabus points

1.7.4.1—Power as work done per unit time or

[Maximum number: 1]

Four electric motors do the same quantity of work when they lift a weight of 10 N through the same distance.

The times taken by each motor to lift the weight are shown.
What is the time taken by the motor which produces the most power?

1.5 s

6.0 s

15 s

60 s

[Maximum number: 3]

Fig. 9.1 shows a mobile phone (cell phone) being charged on a wireless charging plate.

Fig. 9.1

The maximum energy stored in the battery of the mobile phone is 0.012 kWh .

The charging plate in Fig. 9.1 has a useful output power of 15 W . The phone manufacturer claims that the battery can be charged to 50\% capacity in less than 30 minutes.

Show that this claim is true.

50% charged $=\left(4.3 \times 10^{4} / 2=\right) 2.15 \times 10^{4}(\mathrm{~J})$ OR 63% charged in 30 min
OR (50\% charged in t= ) 24 min
$P=E / t \mathbf{OR}(t=) E / P \mathbf{OR} 2.15 \times 10^{4} / 15(\mathrm{~s})$

OR energy provided in $30 \mathrm{~min}=(15 \times 30 \times 60=) 2.7 \times 10^{4}(\mathrm{~J})$ $2.7 \times 10^{4}>2.15 \times 10^{4}$ OR 63 %>50 % OR $30 \mathrm{~min}>24 \mathrm{~min}$

[Maximum number: 2]

A volume of $0.0024 \mathrm{~m}^{3}$ of oil is heated in a pan for 7.0 min . The temperature of the oil increases from $20^{\circ} \mathrm{C}$ to $180^{\circ} \mathrm{C}$ .

The density of the oil is $910 \mathrm{~kg} / \mathrm{m}^{3}$ . The specific heat capacity of the oil is $2000 \mathrm{~J} /\left(\mathrm{kg}{ }^{\circ} \mathrm{C}\right)$ .

Calculate the power required to supply the energy calculated in (b)(ii).

power =

1700 W
( P= ) E / t OR $700000 / 7 \times 60$ OR $704000 / 7 \times 60$ OR $698880 / 7 \times 60$

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CAIE IGCSE Physics 1.7.4 Power Topic Practice

Covered syllabus points

Question 1

Question 2

Question 3