Edexcel A-Level Physics AS Unit 2 Waves and Electricity

Practise Edexcel A-Level Physics AS Unit 2 Waves and Electricity with circuit calculations, resistance explanations, waves and power data.

Covered syllabus points

2.3 - Waves and Particle Nature of Light 2.4 - Electric Circuits

[Maximum number: 1]

The time period of a wave decreases.
Which of the following properties of the wave increases?

amplitude

frequency

speed

wavelength

[Maximum number: 13]

The circuit contains three identical resistors and switches X and Y. Each resistor is wire of diameter $0.181\,\mathrm{mm}$ and length $55.0\,\mathrm{cm}$ , with resistivity $1.10\times10^{-6}\,\Omega\,\mathrm{m}$ at room temperature.

Figure for Question Unit 2: Waves and Electricity question 2 — Edexcel A-Level Physics AS

(a)

Show that the resistance of one resistor at room temperature is about $24\,\Omega$ .

[ 3 ]

Use $A=\pi r^2$ and $R=\rho l/A$ .
$A=\pi(0.0905\times10^{-3})^2=2.57\times10^{-8}\,\mathrm{m^2},$ $R=\frac{(1.10\times10^{-6})(0.550)}{2.57\times10^{-8}}=23.5\,\Omega.$

(b)

A student suggests that the maximum power output from the resistors in this circuit will be greater than 12 W .

Assess whether the student's suggestion is correct.

[ 4 ]

Maximum power occurs at minimum total resistance. With X and Y closed, $R_{tot}=(1/47+1/23.5)^{-1}=15.7\,\Omega$ . Thus $P=V^2/R=12.0^2/15.7=9.2\,\mathrm{W}$ , less than $12\,\mathrm{W}$ , so the suggestion is incorrect.

(c)

Switch X was open and switch Y was closed.

[ 6 ]

(i)

Calculate the number of conduction electrons passing through the resistor each second immediately after switch Y is closed.

Number of electrons =

[ 3 ]

Immediately after closing Y, $I=V/R=12.0/23.5=0.511\,\mathrm{A}$ . In one second $Q=It=0.511\,\mathrm{C}$ , so
$N=Q/e=0.511/(1.60\times10^{-19})=3.2\times10^{18}.$

(ii)

After switch Y had been closed for a few minutes, the power dissipated by the resistor decreased.

Explain why.

[ 3 ]

The resistor temperature rises, so its resistance rises. Since $P=V^2/R$ for fixed supply voltage, the dissipated power decreases.

[Maximum number: 8]

A student investigated the reflection of microwaves from a metal plate and a glass plate. The metal plate reflects microwaves and the glass plate partially reflects microwaves.

A plan view of the apparatus is shown.

The metal plate, the transmitter and the receiver were kept in fixed positions. The value of d was varied by moving the glass plate.

Figure for Question Unit 2: Waves and Electricity question 3 — Edexcel A-Level Physics AS

(a)

As d varied, the intensity of the microwaves detected by the receiver varied.

Explain why.

[ 3 ]

(b)

The student recorded values of d when the receiver showed a maximum value of intensity.

He recorded d for a sequence of five maxima.

Maxima | 1 | 2 | 3 | 4 | 5
d / cm | 9.9 | 11.1 | 12.7 | 13.9 | 15.4

Figure for Question (b) — Edexcel A-Level Physics AS

[ 5 ]

(i)

Determine the wavelength of the microwaves being transmitted.

Wavelength =

[ 3 ]

(ii)

Calculate the frequency of the microwaves being transmitted.

Frequency =

Figure for Question (ii) — Edexcel A-Level Physics AS

[ 2 ]

[Maximum number: 1]

The cell in a solar-powered lamp stores 6.0 kJ of energy.
The lamp is switched on and the cell discharges fully. The cell has a constant e.m.f. of 1.5 V.
Which of the following is the charge flowing through the lamp during discharge?

250 C

900 C

4000 C

9000 C

All question bank results loaded

Covered syllabus points

Unit 2: Waves and Electricity question 1

Unit 2: Waves and Electricity question 2

Question (a)

Question (b)

Question (c)

Question (i)

Question (ii)

Unit 2: Waves and Electricity question 3

Question (a)

Question (b)

Question (i)

Question (ii)

Unit 2: Waves and Electricity question 4