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Ele
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Pag
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(ii)
Calculate the resistance of the wire AC
resistance = ........................... Ω
(b)
[3]
Use your answer to (b)(ii) to answer these questions.
(i)
Calculate the resistance per metre of this wire?
resistance = ......................... Ω / m
(ii)
Calculate the length of wire the laboratory technician needs to make a 64 Ω resistor.
length = ................................... m
Electricity 1
[3]
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Ex
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Pag
(e) In the space below draw a circuit diagram which shows P, Q and R
connected so that they will all work at normal brightness.
[
[1]
Electricity 1
Page 8
Exteension 2
9
9
Electricity 1
Page 9
Answers
Core 2
= V/I = 12/1.5 = 8Ω
(a)
R
(b)(i)
12 V 0.75 A (ii)
16 Ω
(c)(i)
16 Ω/m (ii)
4m Core 3
(a)
Straight line through the origin (b)
Resistance = gradient Alternative to practical 1
(a)
0 – 10 Ω
(b)
a line drawn between 6.2 and 6.4
c(i)
3.4 Ω
(ii) 0.2 Ω
(d)
(e)
connect a variable resistor in series
Alternative to practical 2
(a)
X = variable resistor / rheostat
Y = ammeter
(b)
to change the value of the current
(c)
set X to maximum value, close switch
adjust X to obtain desired value of I
measure I and V
repeat settings for a check / zero meters
(d)
Full Scale Deflection 1 V (maximum V = 9.5 x 0.1 = 0.95 V)
Extension 1
Electricity 1
Page 10
R=VI=6Ω
(a)
(b)
combined resistance of P and Q = 3 Ω
whole resistnance of circuit = 9 Ω
(c)
I = V / R = 1.3 Ω
(d)
the voltage across R is less than 12 V / low / 8 V or the current through R is
less than 2 A
the currents through P and Q are equal / voltage across P and Q is equal
the current through P and Q is less than through R or the potential difference
across P and Q is less than across R
(e)
the diagram should show P, Q and R in parallel
Extension 2
(a)
I = P /V = 1.5 A
(b)(i) R = V / I = 8 Ω
(ii) 6 V
(c)(i) Dimmer
(ii) more resistance in circuit
less current
(d) (i) 4 Ω
(ii) 8 Ω
Electricity 1
Page 11