Electrostatics and Capacitors Generix Content - Electrostatics and Capacitors
HOME

EXAMS

JAMB

WAEC

CONTENTS

SIGN IN

JOIN NOW
"Electrostatics and Capacitors" question number distribution across years
loading...
Search "Electrostatics and Capacitors" on the following sites online
 
Physics index on skoool nigeria
 
JAMB questions for "Physics :: Electrostatics and Capacitors"
Q1
Three cells each of e.m.f. 1.5V and internal resistance 2.5Ω are connected as shown in the diagram. Find the net e.m.f. and the internal resistance.
A
4.5V, 0.83Ω
B
4.5V, 7.50Ω
C
1.5V, 0.83Ω
D
1.5V, 7.50Ω
E
Q2
If two charged plates are maintained at a potential different of 3k V, the work in taking a charge of 600 µC across the field is
A
1.8J
B
18.0J
C
0.8J
D
9.0J
E
Q3
A 120 V, 60W lamp is to be operated on 220 V a.c. supply mains. Calculate the value of non-inductive resistance that would be required to ensure that the lamp is run on correct value
A
200Ω
B
300Ω
C
500Ω
D
100Ω
E
Q4

The instataneous value of the induced e.m.f as a function of time is ε = ε0 sin ωt where ε0 is the peak value of e.m.f. The instantaneous value of the e.m.f., one quarter of the period, is

A

ε⁄ 4

B

ε0

C

0

D

ε⁄ 2

E
Q5

A conductor has a diameter of 1.00mm and length 2.00m. If the resistance of the material is 0.1Ω,its resistivity is

A

2.55 x 102 Ωm

B

2.55 x 105 Ωm

C

3.93 x 10-8 Ωm

D

3.93 x 10-6 Ωm

E
Q6
From the diagram above, the inductive reactance and the resistance R are respectively
A
25Ω and 51Ω
B
20Ω and 50Ω
C
10Ω and 50Ω
D
50Ω and 45Ω
E
Q7
The capacitance of a parallel-plate capacitor when in air is 3 μF and in the presence of a dielectric material 6 μF. The dielectric constant is 
A
9
B
18
C
3
D
2
E
Q8
If the capacity of a capacitor is C= εA/d, which of the following parameters is varied when a variable capacitor is used for tuning radio sets? 
A
Constant (ε) and area 
B
Distance only 
C
Area and distance 
D
Constant (ε) only 
E
Q9
The production and type of charge of a body can only be accounted for by the 
A
deficiency or surplus of neutrons 
B
equilibrium in protons and neutrons 
C
deficiency or surplus of protons 
D
deficiency or surplus of electrons 
E
Q10
A cell of internal resistance r is connected to an external resistor R. The condition for maximum power transfer is 
A
R > r
B
R
C
R = 2r
D
R = r 
E
Q11
In an a.c circuit that contains only a capacitor, the voltage lags behind the current by 
A
90°
B
180°
C
60°
D
30°
E
Q12
If two inductors of inductances 3H and 6H are arranged in series, the total inductances is 
A
18.0 H
B
9.0 H
C
2.0 H
D
0.5 H
E
Q13

The resistance of a piece of wire of length 20m and cross-sectional area 8 x 10-6m2 is

A

8.0 x 10-12NC-1

B

8.0 x 109NC-1

C

4.0 x 109NC-1

D

4.0 x 10-11NC-1

E
Q14
If the distance between two point charges is increased by a factor of four, the magnitude of the electrostatic force between them will be 
A
1/2 of its former value 
B
1/4 of its former value 
C
1/16 of its former value 
D
4 times its former value 
E
Q15
In the circuit of a transistor beside, the terminals P,Q, and R represent
A
COLLECTOR, EMITTER, and BASE
B
EMITTER, BASE and COLLECTOR
C
BASE, EMITTER, and COLLECTOR
D
BASE, COLLECTOR, and EMITTER
E
Q16
The figure below shows three capacitors 2µF, 3µF and 6µF connected in series. If the p.d across the system is 12V, the p.d across the 6µF capacitor is
A
4V
B
6V
C
12V
D
2V
E
Q17
An a.c circuit of emf 12V has a resistor of resistance 8Ω connected in series to an inductor of inductive reactance 16Ω and a capacitor of capacitive reactance 10Ω. The current flow in the circuit is 
A
1.4 A
B
1.2 A
C
12.0A
D
14.0A
E
Q18

In a tuned radio receiver R, L, C series circuit for resonance, the inductive and capacitive reactance XL and XC respectively are related as

A

XL = XC

B

XL  = 1/2 Xc

C

XL = 1/2XC

D

X= 2XC

E
Q19
The instrument used for securing a large number of similar charges by induction is called 
A
electrophorus 
B
capacitor 
C
proof-plane 
D
electroscope 
E
Q20
Given three capacitors 0.3μF, 0.5μF and 0.2μF, the joint capacitance when arranged to give minimum capacitance is 
A
0.1μF
B
0.3μF
C
1.0μF
D
0.5μF
E
Q21
A cell whose internal resistance is 0.5Ω delivers a current of 4 A to an external resistor. The lost voltage of the cell is 
A
1.250V
B
2.000V
C
8.000V
D
0.125V
E
Q22

In the diagram beside, what would happen to the current, I, if another resistor, R2, is connected in parallel to R1

A

it will decrease if R2 is greater than R1

B

It will increase because the equivalent resistance will increase

C

It will decrease if R2 is less than R1

D

It will increase because the effective resistance will decrease

E
Q23
A wire of 5Ω resistance is drawn out so that its new length is two times the original length. If the resistivity  of the wire remains the same and the cross-sectional area is halved, the new resistance is   
A
20Ω
B
5Ω
C
40 Ω
D
10Ω
E
Q24
A positively charged rod X is brought near an uncharged metal sphere Y and is then touched by a finger with X still in place . When the finger is removed, the result is that Y has 
A
a negative charge and a positive potential 
B
no charge and a zero potential
C
a negative charge and a negative potential 
D
a positive charge and a zero potential 
E
Q25
From the diagram below, determine the value of the resistance X.
A
9Ω
B
12Ω
C
15Ω
D
6Ω
E
Q26

The energy stored in a capacitor of capacitance 10μC is

A

4 x 10-3 J

B

5 x 10-4 J

C

5 x 104 J

D

4 x 102  J

E
Q27
An electric iron is rated 1000 W, 230 V. What is the resistance of its element? 
A
57.6 Ω
B
55.9  Ω
C
52.9 Ω
D
51.9 Ω
E
Q28
A transistor is used in the amplification of signals because it 
A
allows doping 
B
contains electron and hole carriers 
C
consumes a lot of power
D
controls the flow of current 
E
Q29
The carbon-granule microphone works on the  principle of change in 
A
voltage 
B
inductance 
C
resistance 
D
capacitance 
E
Q30
At what frequency would a capacitor of 2.5μF used in a radio circuit have a reactance of 250 Ω?
A
800Hz  π
B
200π  Hz
C
2000 π  Hz
D
 π/800    Hz
E
Q31
A cell of internal resistance r supplies current to a 6.0Ω resistor and its efficiency is 75%. Find the value of r.
A
8.0Ω
B
4.5Ω
C
2.0Ω
D
1.0Ω
E
Q32
A capacitor of 20 x 10-12F and an inductor are joined in series. The value of the inductance that will give the circuit a resonant frequency of 200 kHz is 
A
1/8 H
B
1/16 H
C
1/32 H
D
1/64 H 
E
Q33
At resonance, the phase angle in an a.c. circuit is 
A
180°
B
90°
C
60°
D
E
Q34
The current through a resistor in an a.c circuit is given as 2 sin wt. Determine the d.c equivalent of current 
A
2√2 A
B
2A
C
√2A
D
1A/ √2
E
Q35
A transistor functions mainly as a
A
charge storer and a switch 
B
switch and an amplifier 
C
rectifier and an amplifier
D
charge storer and an amplifier 
E
Q36

The diagram beside shows three capacitors, C1, C2, and Cof capacitances 2µF, 6µF and 3µF respectively. The potential differences across C1, C2, and C3 respectively are

A

6V, 4V and 2V

B

6V, 2V and 4V

C

4V, 6V and 2V

D

2V, 6V and 4V

E
Q37
The diagram below shows two capacitors P and Q of capacitance 2µF and 4µF respectively connected to a d.c source. The ratio energy stored in P to Q is
A
1:4
B
1:2
C
2:1
D
4:1
E
Q38
A cell of internal resistance 0.01Ω can be measured accurately using the 
A
Ohm- meter
B
potentiometer
C
electroscope 
D
metre bridge 
E
Q39
The diagram below shows two capacitors P and Q of capacitances 5µF and 10µF. Find the charges stored in P and Q respectively.
A
200µC and 100µC
B
100µC and 200µC
C
4µC and 2µC
D
2µC and 4µC
E
Q40
Four cells each of e.m.f. 1.5 V and internal resistance of 4Ω are connected in parallel. What is the effective e.m.f and internal resistance of the combination ?
A
6.0 V, 16 Ω
B
6.0V, 1Ω
C
1.5 V , 4 Ω
D
1.5V, 1Ω
E
Q41
At what frequency would a 10 H inductor have a reactance of 2000Ω ?
A
π/200 Hz
B
π/100 Hz
C
100/π Hz
D
100πHz
E
Q42
In a series R-L-C circuit at resonance, the voltages across the resistor and inductor are 30 V and 40 V respectively. What  is the voltage across the capacitor?
A
30 V
B
40 V
C
50 V
D
70 V
E
Q43

In the circuit below, the potential across each capacitor is 100V. The total energy stored in the two capacitors is

A

3.0 X 104 J

B

3.0 X 10J

C

2.5 X 10-2 J

D

6.0 X 10-3 J

E
Q44
In the circuit below, the ammeter reads a current of 5.0A when R=8Ω and reads 7.0A when R=5Ω. The value of the unknown resistance X is
A
10.0Ω
B
7.5Ω
C
5.0Ω
D
2.5Ω
E
Q45

In the diagram below, if the internal resistance of the cell is zero, the ratio of the powers P1 and P2 dissipated by Rand R2 respectively, is

A

R2/R1

B

R/ R2

C

R1 + R2 /R1

D

R+ R2 /R2

E
Q46
The total resistance measured at PQ in the diagram above is
A
18.0 Ω
B
11.0 Ω
C
4.0 Ω
D
2.0 Ω
E
Q47

A parallel plate capacitor has a common plate area of 5 x 10-8 m2 and plate separation of 2 x 10-3 m . Assuming free space, what is the capacitance? ( Eo = 9.0 X 10-12 C2 N-1 M-2 )

A

2.25 x 10-1 F

B

4.50 x 10-17 F

C

2.25 X 1016 F

D

4.50 x 10-16 F

E
Q48
Which of the figures below shows the correct distribution of charges on an isolated positively charged hollow metal?
A
B
C
D
E
Q49
Three electric cells each of e.m.f. 1.5 V and internal resistance 1.0Ω are connected in parallel across an external resistance of 2/3 Ω. Calculate the value of the current in the resistor.
A
0.5 A
B
0.9 A
C
1.5A
D
4.5A
E
Q50
A galvanometer of internal resistance 50Ω has a full scale deflection for a current of 5 mA. What is the resistance required to convert it to a voltmeter with full scale deflection of 10 V? 
A
1 750 Ω
B
1950 Ω
C
2000 Ω
D
2 500 Ω 
E
Q51
In a meter bridge experiment, two resistors 2 Ω and 3 Ω occupy the left and right gaps respectively. Find the balance point from the left side of the bridge. 
A
20 cm
B
40 cm
C
60 cm
D
80 cm
E
Q52

Two 50μF parallel plate capacitors are connected in series . The combined capacitor is then connected  across a 100-V battery. The charge on each plate of the capacitor is

A

5.00 X 10-5 C

B

2.50 x 10-3 C

C

1.25 x 10-3 C

D

1.00 x 10-2  C

E
Q53
The purpose of a dielectric material in a parallel plate capacitor is to 
A
increase its capacitance 
B
decrease its capacitance
C
insulate the plates from each other
D
increase the magnetic field between the plates 
E
Q54
An alternating source is connected in series to a capacitor of capacity reactance of 103√3 and a resistor of resistance 103Ω. The impedance of the circuit is 
A
2 000 √3 Ω
B
2000  Ω
C
1000 √3 Ω
D
1000 Ω
E
Q55
The resultant capacitance in the figure below is
A
15.0 µF
B
9.8 µF
C
1.3 µF
D
0.8 µF
E
Q56
In the circuit diagram below, calculate the current in the 12 -Ω resistor if the cell has an e.m.f of 12V and an internal resistance of 1Ω
A
0.8A
B
1.0A
C
1.6A
D
2.4A
E
Q57
A capacitor 8 µF, is charged to a potential difference of 100V. The energy stored by the capacitor is 
A
1.0 x 104 J
B
8.0 x 10 J
C
1.25 X 10 J
D
4.0 X 10-2 J
E
Q58

Two resistors R1 = 4Ω and R2 =5Ω, are connected in parallel across a potential difference. If P1 and Prepresent the power dissipated in R1 and R2 respectively, then the ratio P1 : P2 is

A

4 : 5

B

5 : 4

C

16 : 25

D

25 : 16

E
Q59

A parallel plate capacitor of area 10cm2 in vacuum has a capacitance of 10-2 µF. What is the distance between the plates ? (εo=9 x 10-12 Fm -1)

A

9 x 10-13 m

B

9 x 10-7 m

C

9 x 10-3 m

D

9 x 10m

E
Q60
A 40 W instrument has a resistance of 90Ω. On what voltage should it be operated normally? 
A
60 V 
B
150 V 
C
225 V
D
3600 V 
E