CAIE A-Level Physics A2 20.5.5 Faradays…nduction

[Maximum number: 12]

(a)

State Faraday's law of electromagnetic induction.

[ 2 ]

(b)

Fig. 7.1 shows a coil at rest in a uniform magnetic field that is parallel to the axis of the coil.

Fig. 7.1

The coil is connected to a centre-zero voltmeter.

The flux density B of the uniform magnetic field varies with time t as shown in Fig. 7.2.

Fig. 7.2

The coil consists of 340 turns, each of cross-sectional area $3.2 \times 10^{-4} \mathrm{~m}^{2}$ .

[ 10 ]

(i)

Determine the maximum rate of change of magnetic flux linkage in the coil.
maximum rate of change of flux linkage = $\mathrm{Wbs}^{-1}$

[ 3 ]

tangent drawn at steepest point on Fig. 7.2
evidence of multiplication by 340
Marking guidance:

maximum rate of change of flux $=0.82 \mathrm{~Wb} \mathrm{~s}^{-1}$

(iii)

Fig. 7.3

[ 3 ]

sinusoidal curve of period 2.0 ms from t=0 to t=6.0 ms

all peaks at

+V_0

and all troughs at

-V_0

line showing

V=0

at (and only at) t=0, 1.0, 2.0, 3.0, 4.0, 5.0 and 6.0 ms

(iv)

V=A\sin Bt

A=\underline{\hspace{3cm}}\ \mathrm{V}\qquad B=\underline{\hspace{3cm}}\ \mathrm{rad\,s^{-1}}

[ 3 ]

A=0.82\ \mathrm{V}

or A has same numerical value as answer in (b)(iii), with unit V

B=\frac{2\pi}{2.0\times10^{-3}}

=3100\ \mathrm{rad\,s^{-1}}

CAIE A-Level Physics A2 20.5.5 Faradays and Lenzs Laws of Electromagnetic Induction Topic Practice