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JAMB questions for "Physics :: Electronics, Electricity and Electrical Energy"
Q1

Two long parallel wires X and Y carry currents 3A and 5A respectively. If the force experienced per unit length by X is 5 x10-5 N, the force per unit length experienced by wire Y wire is

A

5 x 10-5 N

B

5 x 10-4 N

C

3 x 10-6 N

D

3 x 10-5 N

E
Q2

118.8cm-2 surface of the copper cathode of a voltameter is to be coated with 10-3 thick copper of density 9 x 10-3 kgm-3. How long will the process run with 10A constant current?

A

15.0 min

B

5.4 min

C

20.0 min

D

10.8 min

E
Q3

A 40 kW electricity cable is used to transmit electricity through a resistor of resistance 2.0Ω at 800 V. The power loss as internal energy is

A

5.0 x 103 W

B

4.0 X 103 W

C

5.0 x 102 W

D

4.0 x 102 W

E
Q4
Lenz's law is a law of the  conservation of
A
electric current
B
momentum
C
electric charge
D
energy
E
Q5

A charge 50 µC has an electric field strength of 360 NC-1 at a certain point. The electric strength due to another charge 120 µC kept at the same distance apart and in the same medium is

A

18 NC -1

B

144 NC-1

C

864 NC-1

D

150 NC-1

E
Q6
The instrument that measures both a.c and d.c is
A
an inverter
B
a moving iron ammeter
C
a current balance
D
a moving coil ammeter
E
Q7

Which of the following diagrams represents correctly an n-p-n transistor?

A
B
C
D
E
Q8
The battery connection that permits current to flow across a p- n junction is called
A
forward biased
B
rectification
C
amplification
D
reverse biased
E
Q9
A  p - n junction diode is used as
A
a rectifier in an a.c circuit
B
a rectifier in a.d.c circuit
C
an amplifier in an a.c circuit
D
an amplifier in a d.c circuit
E
Q10
When the base current of a common-emitter transistor is kept at zero , it operates in the
A
active- on region
B
saturation region
C
cut-off region
D
breakdown region
E
Q11
An ammeter of resistance 5 &#937; has a full-scale deflection when a current of 50 mA flows in it. The value of the resistor required to adapt to measure a current of 5 A is
A
5.00 &#937;
B
0.05&#937;
C
19.80 &#937;
D
0.25 &#937;
E
Q12
An electric heater with a p.d of 240 V connected across its terminal has a total resistance of 960 &#937;. Find the power rating of the heater
A
0.25 W
B
60.00 W
C
38.40 W
D
4.00 W
E
Q13
The main purpose of the transformer in an a.c radio set is to
A
step down the voltage
B
convert energy from a.c to d.c
C
step up the voltage
D
E
Q14
When an a.c voltage is applied to a capacitor, no power is consumed because the current
A
lags behind the voltage by 90°
B
C
and voltage are 180° out of phase
D
and voltage are in phase
E
Q15
The electrolyte in the Nickel -iron (Nife) accumulator is
A
copper tetraoxosulphate (VI) solution
B
potassium hydroxide solution
C
ammonium chloride solution
D
dilute tetraoxosulphate  (VI) acid
E
Q16
When a certain  a.c supply is connected to a lamp, it lights with the same brightness as it does with a 12 V d.c battery . The r.m.s . value of the a.c supply is
A
8.5 V
B
3.5 V
C
12.0 V
D
17.0 V
E
Q17
During electrolysis, 2.0 g of a metal is deposited using a current of 0.5 A in 3 hours. The mass of the same metal which can be deposited using a current of 1.5A in 1 hour is
A
20 g
B
0.5g
C
3.0 g
D
1.0g
E
Q18
A transformer is rated 240 V . If the primary coil is 4000 turns and the secondary voltage 12 V, determine the number of turns in the secondary coil.
A
250
B
100
C
150
D
200
E
Q19
Which of the following materials is a conductor ?
A
Plastic
B
Sodium
C
Wax
D
Glass
E
Q20
The charge carriers in gases are
A
ions only
B
electrons and holes
C
electrons only
D
electrons and ions
E
Q21
The current in a reverse-biased junction is due to
A
electrons
B
majority carriers
C
holes
D
minority carriers
E
Q22

The electric field intensity in place  where a charge 1010 C experiences a force of 0.4 N is

A

8.0 X 1012NC-1

B

8.0 x 109NC-1

C

4.0 x 109NC-1

D

4.0 x 10-11NC-1

E
Q23
An electric device is rated 2000 W, 250 V. The correct fuse rating of the device is
A
8A
B
9A
C
7A
D
6A
E
Q24
A car battery rated 45 AH is charged with a charger whose rating is 2.5A. How long will it take to charge the battery fully?
A
20 hrs
B
10 hrs
C
25 hrs
D
18 hrs
E
Q25
In the diagram below, the ratio if the electric power dissipated in the 6&#937; and 3&#937; resistors respectively is
A
2:1
B
2:3
C
1:3
D
1:2
E
Q26
A generator manufacturing company was contracted to produce an a.c dynamo but inadvertently produced a.d.c dynamo. To correct this error, the
A
armature coil should be made of silver
B
commutator should be replaced with slip rings
C
commutator should be replaced with slit rings
D
armature coil should be made of aluminium
E
Q27
A moving-coil galvanometer has a full-scale deflection of 3A equivalent to 30° deflection. The sensitivity of the instrument is
A
33.0
B
0.1
C
90.0
D
10.0
E
Q28
In a reverse biased junction diode, current flows in by
A
positive holes alone
B
majority carriers
C
electrons alone
D
minority carriers
E
Q29

The energy stored in an inductor of inductance 5mH when a current of 6A flows through it is

A

9.0 X 10-3J

B

9.0 X 10-2 J

C

1.4 X 10-2 J

D

1.8 X 10-2 J

E
Q30
Which of the following is an electrolyte?
A
Paraffin
B
Sugar solution
C
Grape juice
D
Alcohol
E
Q31

If 16mA of current flows through a conductor in one second, the number of electrons transported per second is

A

1.00 x 1020

B

2.56 x 10-18

C

2.56 x 10-17

D

1.00 x 1017

E
Q32
Electrical appliances in homes are normally earthed so that
A
the appliances are maintained at a lower p.d than the earth
B
both the a.c and d.c sources can be used
C
a person touching the appliances is safe from electric shock
D
the appliances are maintained at a higher p.d than the earth
E
Q33
In the diagram below, if each of the resistors can dissipate a maximum of 18W without becoming excessively heated, what is the maximum power the circuit can dissipate?
A
9W
B
27W
C
5W
D
18W
E
Q34
The most suitable cell used for short interval switches in electric bells is a
A
nickel iron accumulator
B
C
Daniel cell
D
Leclanché cell
E
Q35

A circuit has an area of 0.4m2 and consists of 50 loops of wire. If the loops are twisted and allowed to rotate at a constant angular velocity of 10 rad s-1 in a uniform magnetic field of 0.4T, the amplitude of the induced voltage is

A

80 V

B

20 V

C

8V

D

16 V

E
Q36
When an alternating current given by 1 = 10sin (120&#960;) passes through a 12&#937; resistor, the power dissipated in the resistor is
A
120W
B
30W
C
600W
D
1200W
E
Q37

In the calibration of an ammeter using Faraday's laws of electrolysis, the ammeter reading is kept constant at 1.20A. If 0.990g of copper is deposited in 40 minutes, the correction to be applied to the ammeter is

A

0.05A

B

0.06A

C

0.03A

D

0.04A

E
Q38
The electric field between two-point charges is shown in the diagram beside. What types of charges are at X and Y?
A
X is positive and Y is negative
B
X is negative and Y is positive
C
Both X and Y are positive
D
Both X and Y are negative
E
Q39
An electric cell with nominal voltage E has a resistance of 3 &#937; connected across it. If the voltage falls to 0.6E, the internal resistance of the cell is
A
4 &#937;
B
3  &#937;
C
2 &#937;
D
1 &#937;
E
Q40
When connected to a mains of 250V, the fuse rating in the plug of an electric device of 1 kW is
A
4A
B
2A
C
5A
D
3A
E
Q41
A current of 0.5 A flowing for 3 h deposits 2g of a metal during electrolysis. The quality of the same metal that would be deposited by a current of 1.5 A flowing in 1h is
A
10 g
B
18 g
C
2 g
D
6 g
E
Q42
From the generating station to each substation power is transmitted at a very high voltage so as to reduce
A
eddy current loss
B
hysteresis loss
C
heating in the coils
D
magnetic flux leakage
E
Q43
Which of the following statements is true of the properties of a moving coil galvanometer?
A
There are strong hair springs to give a large control couple
B
It has a small number of turns of coil
C
The coil has a small area
D
There is a strong  permanent magnet to give high magnetic flux
E
Q44

Which of the following graphs shows the correct vector diagram for the circuit above?

A
B
C
D
E
Q45
In the diagram below, determine the r.m.s current
A
80A
B
60A
C
48A
D
31A
E
Q46

A student is at a height 4 m above the ground during a thunderstorm. Given that the the potential difference between the thundercloud and the ground is 107V, the electric field created by the storm is

A

4.0 x 107 NC-1

B

1.0 x 107 NC-1

C

2.5 x 106 NC-1

D

2.0 x 106 NC-1

E
Q47
In a Daniell cell, the depolarizer, positive and negative electrodes are respectively
A
manganese dioxide, carbon and zinc
B
potassium hydroxide, nickel and iron
C
copper sulphate , copper and zinc
D
E
Q48
A cell can supply currents of 0.4 A and 0.2 A through a 4.0&#937; and 10.0&#937; resistors respectively. The internal resistance of the cell is
A
1.0 &#937;
B
1.5&#937;
C
2.0&#937;
D
2.5&#937;
E
Q49
A resistance R is connected across the terminal of an electric cell of internal resistance 2&#937; and the voltage was reduced to 3/5 of its nominal value. The value of R is
A
6&#937;
B
3&#937;
C
2&#937;
D
1&#937;
E
Q50
The cost of running five 60 W lamps and four 100W lamps for 20 hours if electrical energy costs N10.00 per k Wh is
A
&#8358; 120.00
B
&#8358;140.00
C
&#8358;160.00
D
&#8358;280.00
E
Q51

A bread toaster uses a current of 4 A when plugged in a 240 volts line. It takes one minute to toast slices of bread . What is the energy consumed by the toaster?

A

1.60 x 102 J

B

3.60 x 103 J

C

1.60 x 104 J

D

5.76 x 10J

E
Q52
A working electric motor takes a current of 1.5 A when the p.d across it is 250 V. If its efficiency is 80%, the power output is
A
4.8 W
B
133.0 W
C
300.0 W
D
469. 0 W
E
Q53
The primary coil of a transformer has N turns and is connected to a 120 V a.c power line . If the secondary coil has 1000 turns and a terminal voltage of 1200 volts, what is the value of N?
A
1200
B
1000
C
120
D
100
E
Q54
Energy losses through eddy currents are reduced by using
A
insulted soft iron wires
B
low resistance wires
C
high resistance wires
D
few turns of wire
E
Q55
In the circuit diagram below, the ammeter reads a current of 3A when R is 5&#937; and 6A when R is 2&#937;. Determine the value of X.
A
2&#937;
B
4&#937;
C
8&#937;
D
10&#937;
E
Q56
In the diagram below, the current I is
A
8/3A
B
11/9A
C
9/11A
D
3/8A
E
Q57
The diagram below shows a closed square box of side 0.5m in a uniform electric field E in the direction shown by the arrows. What is the flux &#934; for the box?
A
0.0E
B
0.2E
C
0.5E
D
2.0E
E
Q58

Which of the following graphs correctly represents the variation of mass of a given material deposited with time for constant current in Faraday's law of electrolysis?

A
B
C
D
E
Q59

In the diagram below, the values of V1 and Vare respectively

A

IV and V

B

1/3V and 2/3V

C

1/3 and 2/3V

D

IV and 2/3V

E
Q60

An electron of charge 1.6 X 10-19 C and mass 9.1 X 10-31 kg is accelerated between two metal plates with a velocity of 4 x 107 ms-1, the potential difference between the plates is

A

4.55 x 101 V

B

9.10 x 101 V

C

4.55 x 102  V

D

4.55 X 103 V

E