Download Electricity and Electronics Revision Questions Multiple Choice and

Electricity and Electronics Revision
Questions
Multiple Choice and Short Answer
Please Note:
These questions come from an earlier
version of the syllabus.
Some of these questions represent very
difficult problem solving.
Not all areas of the course are covered, for
example there are no questions on
operational amplifiers.
Answers are at the end.
1.
Which of the following units is equivalent to a
farad?
A
B
C
D
E
2.
3.
A pupil sets up the circuit shown below.
V
C
CV
C V-1
V C-1
The circuit shown was used in an experiment
to study the charging and discharging of a
capacitor. The voltmeter has a very high
resistance.
If the ammeter P reads 2 A, then the voltage of
the d.c. supply is
A
B
C
D
E
4.
The graph below was drawn using results
obtained.
14 V
19 V
21 V
22 V
34 V.
In the following circuits, each cell has an
e.m.f. of 1.5 V and an internal resistance
of 1 . Each resistor has the same value, 2 .
It is a graph of
A
B
C
D
E
potential difference across the
capacitor against time during charging
current against time during charging
current against potential difference
across capacitor during charging
potential difference across the
capacitor against time during
discharging
current against time during
discharging.
If the resistance of the ammeter in each circuit
is negligible, which two ammeters will show
the same reading?
A
B
C
D
E
A1 and A4
A2 and A5
A3 and A5
A4 and A2
A5 and A1
5.
The power dissipation in the resistor of fig 1 is
100 W.
7.
The diagram shows a source of ions S, and a
grid G beyond which is a collecting plate P.
There is a potential difference V between P
and G so that ions drifting into the space
between P and G are accelerated to P. The
whole apparatus is in an evacuated chamber.
What is the power dissipation in the resistor of
fig 2?
A
B
C
D
E
6.
100 W
200 W
400 W
800 W
1600 W
A 50 Hz a.c. source is connected to an oscilloscope. The trace obtained is shown below.
Which of the following will affect the time an ion
takes to go from G to P?
I
II
III
A
B
C
D
E
The time-base setting is
A
B
C
D
E
2.5 milliseconds per centimetre
5 milliseconds per centimetre
10 milliseconds per centimetre
12.5 milliseconds per centimetre
80 milliseconds per centimetre.
the potential difference V
the mass of the ion
the charge on the ion
I only
II only
I and III only
II and III only
I, II and III
8.
A four-terminal box is connected as shown to
a battery and two milliammeters. The currents
in the two meters are identical.
9.
In the circuit diagram below, C is a 1.0 F
capacitor holding a charge of 10 -5C and R is a
10  resistor.
If the switch is suddenly closed, the initial current flowing in the circuit will be
Which of the circuits A to E below, within the
box, is the only one which will give this
result?
A
B
C
D
E
10.
zero
10-5A
10-1A
1A
10 A.
In the circuit shown the cell has an e.m.f. of
6.0 V and an internal resistance of .
When the switch is closed, the reading on the
ammeter is 2 A. What is the corresponding
reading on the voltmeter?
11.
In the circuit below, the ammeter registers
2 A.
How much energy is dissipated in the resistor
in 1 minute?
12.
A 16-pin package contains 15 identical
resistors connected together as shown.
13.
When another 3.0  resistor is connected in
parallel with the original one, the ammeter
reading changes.
What would be the two readings on the
ammeter?
To test these resistors, an engineer connected
pins together externally and labelled them
terminals P, Q, R, S and T, as shown below.
When he measured the resistance between pin
16 and each of these terminals in turn, the
engineer found the greatest resistance between
pin 16 and
A
B
C
D
E
A cell of e.m.f. 4.0 V and internal resistance
1.0  is used in the following circuit. The
ammeter has negligible resistance.
14.
The diagram below shows an 8 V supply
connected to two bulbs.
terminal P
terminal Q
terminal R
terminal S
terminal T.
In l6s, the electrical energy converted in the
two bulbs is
A
B
C
D
E
2J
4J
8J
32 J
64 J.
15.
In the circuit shown below, point X can be
attached to any of the points L, M, N, P or Q.
16.
An alternating signal is applied to an
oscilloscope which has its time-base set at “1
millisecond per centimetre”. Two complete
waves appear on the screen, which is 4cm
wide.
To which point must X be connected to obtain
a zero reading on the galvanometer G?
A
B
C
D
E
L
M
N
P
Q
The time-base is then altered to “10
milliseconds per centimetre”, with every other
control kept as before.
How many waves will appear on the screen
now?
17.
In the following circuit, the Wheatstone
Bridge is balanced.
18.
Resistors R1, R2 and R3 can be connected to
form the two networks shown in the diagram.
Small adjustments are made to the variable
resistor R3 and the corresponding current
reading in the galvanometer (Ig) is noted.
A graph of the current through the
galvanometer is plotted against R3, the small
change in the resistance of R3.
Which of the following shows that graph?
The total resistances between the terminals P
and Q, of network 1, and X and Y, of network
2, are mainly decided by the value of one
resistor in each network.
These dominant resistors are
19.
Bulb X in the circuit below has a rating 12 V;
24W and is operating under these conditions.
R1 and R2 are of equal resistance.
For balance in this Wheatstone Bridge
arrangement, R3 must have a value of
A
B
C
D
E





20.
Which of the following circuits would be used in an
experiment to illustrate the charging and discharging of a capacitor in a d.c. circuit?
suitable centre—zero ammeter.
A
21.
is a
A capacitor is connected in series with a
variable resistor, a sensitive ammeter, a switch
and a battery, as shown.
After the switch is closed, the variable resistor
R is reduced at a rate which ensures that the
capacitor C has a constant charging current of
2.0 x 10-5 A for a time of 30s. During this
time, the p.d. across the capacitor rises from 0
V to 12V.
What is the capacitance of the capacitor?
A
B
C
D
E
22.
2.0 x I0-4 F
2.4 x 10-4 F
5.0 x I0-5 F
8.0 x 10-6 F
1.7 x 10-6 F
When a 12V, 50Hz a.c. supply is connected to
an oscilloscope the following trace is
obtained.
The time base control of the oscilloscope is set
to move the spot across the screen at
A
B
C
D
E
1 division per 1/600 th of a second
1 division per 1/500 th of a second
1 division per 1/400 th of a second
1 division per 1/200 th of a second
1 division per 1/50 th of a second.
23.
An immersion heater is used to heat water in
an insulated container. An a.c. supply and a
d.c. supply are available which produce the
same rate of heating from the heater.
If the a.c. supply has a peak value of 10V,
then the p.d. of the d.c. supply must be
26.
A 20 V supply, connected to a set of resistors
in series as shown, can be used to provide a
selection of output voltages by suitable choice
of connecting points. The resistance of each
resistor is as shown in the diagram.
Between which two points does the voltmeter
read 8V?
24.
Four resistors are connected to a 6 V supply as
shown.
A
B
C
D
E
27.
LN
MO
KL
KN
LO
A low resistance ammeter and a high
resistance voltmeter are used to measure
resistance R. The resistance of the voltmeter is
known to be about the value of R.
Initially circuit I is used, then circuit II.
What is the potential difference between
points X and Y?
25.
The circuit below shows two 4  resistors in
parallel across a 6 V constant voltage supply.
What changes are there in the meter readings
when circuit II is used?
Calculate the total power developed in this
circuit.
28.
A particular wire wound resistor has a
resistance of 100  when used at a room
temperature of
200C.
30.
In the circuit below, S is a two-way switch
and A is a centre-zero ammeter.
Using wire of the same metal, another resistor
is constructed. Which of the following
combinations of factors would be certain to
give a resistance greater than l00 ?
The switch contact is moved to X then very
quickly to Y. Which of the graphs shows how
the current I in the ammeter varies with time?
29.
When a capacitor of capacitance C is
connected to a supply of potential difference
V, it stores a charge Q.
Which of the following expressions correctly
gives the energy stored in the capacitor?
31.
In the following circuit, the supply maintains a
constant d.c. voltage. When the switch S is
closed, the power delivered to the circuit by
the supply is 30W.
What power is delivered to the circuit by the
supply when the switch is open?
32.
On setting up the following bridge circuit, a
pupil finds that no current flows in the
galvanometer.
What is the resistance of the unknown resistor
R?
33.
An immersion heater is connected to a
constant voltage supply. It is found that 2000J
of energy is required to supply a current of 2
A for 4s through the immersion heater. What
is the potential difference between the ends of
the heater, in volts?
34.
The circuit below is set up in the laboratory
during some practical work in electricity,
using a power supply which has no internal
resistance.
What reading is recorded on the ammeter,
assuming it has no resistance?
A
B
C
D
E
0.05A
0.125A
0.25A
0.50A
1.25A
35.
The diagram shows a circuit used to determine
the e.m.f. E and the internal resistance r of a
cell.
Which graph correctly shows how the
potential difference V across the terminals of
the cell varies with the current I drawn from
it?
36.
In the Wheatstone Bridge circuit below, the
variable resistor R is initially set at 50.0 .
The value of R is then increased in 0.1  steps
up to 51 and the corresponding values of
galvanometer current I are noted. A graph of
galvanometer current I against change in resistance X from the initial value is of the form
37.
In the following circuit, the p.d. across the 16
ohm resistor is 40 volts when switch S is
open.
What is the p.d. across the 16 ohm resistor
when the switch S is closed?
38.
Each cell in the circuit below has an e.m.f. of
2 V and an internal resistance of 1 .
Calculate the current in this circuit.
39.
The diagram shows two charged parallel
plates in a vacuum. The electric field between
the plates is shown by the dashed lines.
An electron starts from rest at G and moves
along one of the paths GH or GI.
Which entry in the table below describes the
motion of the electron, if gravitational effects
are neglected?
40.
The diagram below shows a charged capacitor
C in a circuit with a resistor R and a switch S.
Which one of the following graphs correctly
represents the variation of current I with time t
in the above circuit after S is closed?
41.
The diagram illustrates an experiment to compare the a.c. and d.c. voltages which will produce the same brightness in the lamp.
43.
The circuit diagram below shows a cell of
e.m.f. E and internal resistance r in series with
a resistor R.
Which of the following statements about this
circuit is/are always true?
The circuit is adjusted until the lamp
brightness is the same with either a.c. or d.c.
voltages across it.
The pieces of apparatus marked W, X, Y and
Z are
I
II
III
A
B
C
D
E
44.
42.
The potential divider PQ is set up as shown
below.
The p.d. across the terminals of the cell
is less than the e.m.f. of the cell.
The current in R is less than that in r.
The p.d. across R is less than the
voltage “lost” across r.
I only
I and II only
I and III only
III only
II and III only
In the following circuit, VC is the p.d. across
the capacitor and VR is the p.d. across the
resistor.
When the capacitor is fully charged, which of
the following statements is/are true?
I
II
III
The potential difference across the load
resistor XY is
A
B
C
D
E
3V
5V
9V
13 V
15 V.
A
B
C
D
E
VR has reached its maximum value.
VC has reached its maximum value.
The current from the cell has reached
its maximum value.
I only
II only
III only
I and II only
I,II and III
45.
A manufacturer constructs a capacitor of
parallel metal plates separated by a thin layer
of plastic dielectric. He states that “it has a
maximum working voltage of l0 V”.
Which of the following statements is/are
correct?
I
II
III
A
B
C
D
E
46.
48.
Which of the following circuits has the lowest
resistance between terminals X and Y?
49.
Four resistors, each of resistance 8 , are
connected across a 60 V supply of negligible
internal resistance, as shown below.
A potential difference greater than 10
V may cause the dielectric to break
down.
Above 10 V, the capacitor will still
work but its capacitance will increase.
The capacitor can only be charged by a
supply of e.m.f. 10 V.
I only
II only
III only
I and II only
I and III only
A 20V, 0.5A bulb is connected to a 6V d.c.
supply as shown. The supply has negligible
internal resistance.
If the bulb is to operate at its correct rating,
what must be the value of the resistor R?
47.
The circuit shown consists of a battery of
e.m.f. 10 V and internal resistance 2 
connected to a resistor of value 3  and a high
resistance voltmeter.
What is the power produced in the 3 
resistor?
The p.d. across LM is
A
B
C
D
E
12 V
15 V
20 V
24 V
30 V.
50.
A battery is tested in the following circuit.
52.
An a.c. voltage is applied across the input of
an oscilloscope and the following trace is
seen. The grid lines on the screen are 1 cm
apart.
The corresponding readings of voltage and current are taken at various settings of the variable
resistor and a graph is plotted as shown below.
If the Y-gain control of the oscilloscope is set
at 5 Vcm-1, the r.m.s. value of the a.c. voltage
is
What is the e.m.f. and the internal resistance of
this battery?
51.
A battery of e.m.f. 12V and internal resistance
2 is connected to a 4 resistor as shown.
The readings on the ammeter and voltmeter
are noted.
The 4  resistor is replaced by a 2  resistor.
Which of the following three statements is/are
correct?
I
II
III
A
B
C
D
E
The ammeter reading increases.
The voltmeter reading increases.
The power developed in the resistor
increases
I and II only
I and III only
II and III only
III only
I,II and III
53.
In the following diagram, R is a variable resistor. It
is set at 8000  to balance the Wheatstone bridge.
R is increased gradually from 8000 to
8010.
Which one of the following graphs correctly
illustrates how the current I through the sensitive meter G varies as the resistance of R is
increased?
54.
A pupil uses a transformer to step down mains
voltage to light a lamp. The currents and voltages at various places in the circuit are
indicated below.
What is the percentage efficiency of the transformer in this circuit?
55.
The electron shown in the diagram below is
emitted from an electron gun and then moves
between two charged plates. The direction of
the electric field between these plates is as
indicated.
Assuming that the effects of gravity may be
ignored, which of the following diagrams
correctly indicates the motion of the electron
as it passes through the electric field?
56.
A pupil tries out various arrangements of three
1  resistors between the terminals X and Y
of the following circuit.
57.
In the circuit shown, the resistors are identical,
the battery has negligible internal resistance
and the voltmeter draws negligible current.
Select from the table below a possible correct
set of results for the readings on the voltmeter.
One arrangement gives full-scale deflection on
the ammeter. All the other arrangements give
deflections less than the full-scale deflection.
Which arrangement gives full-scale deflection
on the ammeter?
58.
A signal generator is connected to the Y-plates
of an oscilloscope and the following trace is
seen on the screen.
Each small square on the screen measures 1
cm by 1 cm.
What is the frequency and the peak voltage of
the a.c. signal?
59.
The graph below shows the relationship
between the charge stored on a parallel plate
capacitor and the p.d. across its plates while it
is being charged up to a final voltage.
Which of the following could not be
calculated from the information given on the
graph?
A
B
C
D
E
60.
The capacitance of the capacitor
The final charge stored on the capacitor
The final energy stored on the
capacitor
The final electric field strength
between the plates
The final voltage across its plates
A charged particle is fired between a pair of
charged parallel plates as shown in the
diagram. While passing between the plates,
the electric field deflects it sideways by 1 unit.
A different charged particle, which has double
the charge and four times the mass of the first
particle, is fired with the same velocity
between these plates. The electric field will
deflect it by
A
B
C
D
E
¼ unit
½ unit
1 unit
2 units
4 units
61.
In the potential divider circuit shown below,
the variable resistor allows the potential
difference between X and Y to be varied.
For the values given, what is the maximum
potential difference which can be obtained
across XY?
Answers
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
D
A
B
A
D
B
E
B
D
4V
720 J
A
B
E
D
20
E
D
B
C
C
C
B
6V
18 W
B
E
E
E
B
15 W
200 
250 V
D
C
B
48 V
1A
B
A
D
A
A
B
A
8 
12 W
C
A
D
B
A
A
75 %
C
A
E
E
D
D
8V