Each
of the resistors in
the circuit below
has a resistance R
Ohms. What is their
total resistance (in
terms of R). 

Question
2
a) 
Four identical
resistors are
connected to a
battery of emf 12V and zero internal resistance, as shown below. 



What voltage would a
voltmeter read when
connected across the
following points? 

i) 
A and D 
ii) 
A and B 
iii) 
A and C 
iv) 
B and C 

b) 
A short circuit (a
wire of very low
resistance) is
connected across
points C and D, as
shown below. 



What voltage would a
voltmeter now read
when connected
across the following
points?


i) 
A and D 
ii) 
A and B 
iii) 
A and C 
iv) 
B and C 

Question
3
a) 
Calculate the total
resistance of the
four resistors in
the circuit shown
below. 


b) 
Calculate the total
resistance of the
same four resistors
when a wire of very
low resistance is
connected across
points X and Y. 
Questions 4 to 11 are all about the circuit drawn
below. The cell has zero internal resistance
Question
4
Calculate
the total resistance of the circuit.
Question
5
Calculate
the current
I.
Question
6
Calculate
the voltage across the points A and B.
Question
7
Calculate
the current
I_{1}.
Question
8
How
much charge will pass through the cell in 20s?
Question
9
How much
energy will be converted to heat by the
6
resistor in 5 minutes?
Question
10
Calculate
the power dissipated in the
8
resistor.
Question
11
Calculate
the total amount of energy converted to heat by all the
resistors in 10 minutes
Question
12
Calculate the maximum current which can be
supplied by each of the following batteries 
a) 
a
car battery of emf
=
13·2V
and internal resistance r = 0·15 
b) 
a
battery of eight cells each of emf
= 1·6V
and internal resistance r = 0·4 
Question
13
Two
resistors, R_{1} =
3
and R_{2} =
6,
are connected in parallel with each other. They
are then connected to a battery of emf,
=10V
and internal resistance r =
3.

Calculate 
a) 
the
current flowing through the battery 

b) 
the
current flowing through the
6
resistor. 
Question
14
A battery of emf,
= 6V is connected to two 5 resistors in parallel with each other. If the
current flowing through the battery is 2 A, calculate the internal resistance of the battery.

Question
15
Three 12
resistors are to be connected to a battery of
= 24V
and r = 2.
Draw circuit diagrams showing how the resistors
should be connected in order that the current
flowing through the battery is 
a) 4A 
b)
1·2A 
c)
0·63A 
d)
2·4A 

Question
16
This question is about rms currents and voltages. 

For
the circuit shown above calculate 
a) 
the
rms value of the current,
I 
b) 
the
maximum value of the current 
c) 
the
mean power dissipated in R_{1} 
d) 
the
rms value of the voltage across R_{2}. 
Question
17
A resistor is to be made using wire of diameter 0.2mm. The wire is made of nichrome of resistivity 1.50×10^{6}m. 
a) 
Calculate the length of wire needed to make a resistor of resistance 15.0.

b) 
If the diameter of the wire was measured using a Vernier calliper having a precision of ±0.02mm what is the uncertainty in the value of the resistance made using the wire (state your answer in the usual way: resistance = R ±R ). Ignore any other sources of uncertainty in this calculation. 
c) 
Calculate the power dissipated in the resistor when a current of 1.5A flows through it. 
d) 
The resistor is found to change temperature by 2.4°CW^{1} of power dissipated. After the current (1.5A) has been flowing for a few minutes, the temperature of the resistor will have increased. Given that the temperature coefficient of resistance of nichrome is 4.0×10^{−4}°C^{1}, show that the change in resistance of the resistor is unlikely to cause too many problems. 
Question
18
A thermistor, R_{t} (temperature dependent resistor) is to be used in a potential divider circuit as part of a thermostat. The heater is switched on (by circuits not shown) when the voltage across R_{t} is 1.25V. The graph shows the variation with temperature of the resistance of R_{t}. 
Find the approximate temperature at which the heater will switch on 
a) 
with R = 9k 
b) 
with R = 18k 
