2011 - JAMB Physics Past Questions and Answers - page 4
31
If the charge of electricity is K wh is N4, what is the cost of operating an electrical appliance rated 250 v,2 A for six hours?
A
N28
B
N12
C
N16
D
N24
correct option: b
Energy consumed = power x time = lvt = 2 x 250 x 6hr = 300 wh = 3 kwh but 1 kwh = N4
3 kwh = 3 x N4 = N 12
Users' Answers & Comments32
Under which of the following conditions do gases conduct electricity?
A
Low presssure and low p.d
B
low pressure and high p.d
C
high pressure an low p.d
D
high pressure and high p.d
correct option: b
Under high potential difference and low pressure gases are good conductor of electricity
Users' Answers & Comments33
Two inductors of inductance 4 II and 8 II are arrange in series and a current of 10 A is passed through them. What is the energy stored in them?
A
500 J
B
50 J
C
133 J
D
250 J
correct option: c
Effective inductance
(1)/L = (1)/4 + (1)/8 = (3)/8
∴ L = (8)/3
Energy stored = (1)/2 LI2
= (1)/2 x (8)/3 x 10 x 10 = (400)/3 = 133.3 J
Users' Answers & Comments34
Which of the following materials has an increase in resistance with temperature?
A
water
B
metals
C
wood
D
electrolyte
35
The bond between silicon and germanium is
A
covalent
B
ionic
C
dative
D
electrovalent
correct option: a
Users' Answers & Comments36
A radioactive isotope has a decay constant of 10-5s4. Calculate half life
A
6.93 x 105s
B
6.93 x 105s
C
6.93 x104s
D
6.93 x 104s
correct option: c
T (1)/2 = (0.693)/λ = (0.693)/10-5
= 0.693 x 105
= 6.93 x 104 sec
Users' Answers & Comments37
The electrical properties of germanium can be altered drastically by the addition of impurity. This process is referred to as
A
saturation
B
bonding
C
amplification
D
dopping
correct option: d
Users' Answers & Comments38
If the threshold frequency for tungsten is 1.3 x 1015Hz, what is its work function?
[H = 6.6 x 10-34 Js]
[H = 6.6 x 10-34 Js]
A
8.58 x 10-19 J
B
8.50 x 10-15 J
C
8.58 x 10-17 J
D
8.85 x 10-18
correct option: a
Work function, w = hfo 6.6 x 10-34 x 1.3 x 1015
= 8.58 x 10-19
Users' Answers & Comments39
Which of the following will be applied when a metal Y is used to electroplate another metal X in electrolysis?
A
X is the anode and very high current is used
B
X is the anode and Y is the cathode
C
Y is the cathode and X is the anode
D
Y is the anode and very high current is used
correct option: d
Metals and hydrogen are deposited at the cathode, while non-metals and oxygen are deposited on the anode
∴ metals Y will form the anode which is deposited at the cathode made of x
Users' Answers & Comments40
A
14.0 N
B
10.0 N
C
12.0 N
D
13.0 N
correct option: b
The resultant, R is given by pythagoras rule, R2 = P2 + Q2
= 62 + 82 = 36 + 64 = 100
R = √100 = 10.0N
Users' Answers & Comments