Physics · Oct / Nov 2021 · Paper 41 · Question 8
0625
As printed in the paper
The question as text
A circuit contains two fixed resistors and a light‑dependent resistor (LDR). Fig. 8.1 shows that the power supply is a 9.0 V battery. 450 Ω 800 Ω 9.0 V Fig. 8.1 The current in the 450 Ω resistor is 0.012 A.
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8(a)[1]
Q / t or (rate of) flow of (electric) charge / electrons
I2 – I1
8(b)[1]
(current in the 450 Ω resistor =) ..............................................................
8(c)[4]
(V450 Ω =) IR or 0.012 × 450 or 5.4 (V) or 9.0 – 5.4 or 3.6 (V) seen
(I =) 3.6 / 800 or 0.0045 (A)
(P =) VI or 3.6 × 0.0045 or 3.62 / 800
1.6 × 10–2 W or 16 mW
8(d)[3]
resistance (of LDR) decreases
current (in circuit) increases
or
resistance of parallel pair decreases
p.d. across 800 Ω resistor increases and
or
resistance of parallel pair a smaller fraction
p.d. across
of total resistance and p.d.
450 Ω resistor decreases
across 450 Ω resistor decreases
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