2015 - JAMB Physics Past Questions and Answers - page 5
41
The strength of an electromagnet increase with
A
Increase in the number of turn of the coil
B
Decrease in current with the coil
C
Increase in the distance between the pole
D
Increase in current without the coil
correct option: a
Note: the strength of an electromagnet increase with a decrease in the number of turns of the coil other are(ii) increase in current with in the coil
Users' Answers & Comments42
A platinum resistance thermometer wire has a resistance of 70hms at 0°Cand 7.5 Ohms at 100°C. Calculate the temperature of the wire when the resistance is 7.2 Ohms
A
15°C
B
40°C
C
20°C
D
10°C
correct option: b
R0 = 7Ω , R1 = 7.2 Ω, R2 = 7.5 Ω, Tx = ?
[(X – T100°C) ÷ (R1 - R0)] = [(T100°C – T0°C) ÷ (R2 - R0)]
[(Tx – 0) ÷ (72 – 7)] = [(100 – 0) ÷ (7.5 – 7)]
Tx/0.2 = (100 ÷ 0.5)
Tx = [(0.2 × 100)] ÷ 0.5
= 20/0.5 = 40°C
Users' Answers & Comments[(X – T100°C) ÷ (R1 - R0)] = [(T100°C – T0°C) ÷ (R2 - R0)]
[(Tx – 0) ÷ (72 – 7)] = [(100 – 0) ÷ (7.5 – 7)]
Tx/0.2 = (100 ÷ 0.5)
Tx = [(0.2 × 100)] ÷ 0.5
= 20/0.5 = 40°C
43
Which of the following will increases the boiling point of water?
I. Taking it to a high altitude
II. Dissolving a salt into it
III. Heating it in a sealed flask
IV. Increasing the rate of heat supply
.
I. Taking it to a high altitude
II. Dissolving a salt into it
III. Heating it in a sealed flask
IV. Increasing the rate of heat supply
.
A
I only
B
III & IV only
C
II & III only
D
II only
correct option: b
The boiling point of water can increase, if
1. Heating it in a sealed flask
2. The rate of the heat supply is increased
Users' Answers & Comments1. Heating it in a sealed flask
2. The rate of the heat supply is increased
44
What is the magnitude of the couple which acts on a rotating circular disc of radius 2m, if a constant tangential force of 2N is responsible for the rotation.
A
15Nm
B
25Nm
C
3Nm
D
4Nm
correct option: d
Users' Answers & Comments45
Transformers are designed so that energy losses are reduced to a minimum. This is achieved through those process.
I. Using a soft iron ore
II. Laminating the iron core to reduce energy loses due to eddy current
III. Designing an efficient iron core
I. Using a soft iron ore
II. Laminating the iron core to reduce energy loses due to eddy current
III. Designing an efficient iron core
A
I & II only
B
II only
C
I, II, & III only
D
III only
correct option: c
Fig (I) (II) (III) are they in which a transformer was designed to reduce an energy loses by reducing through this collective designed or efforts
Users' Answers & Comments46
The two liquids which are often used in thermometer on experiment basic is known as
A
Mercury only
B
Alcohol and Water
C
Mercury and Alcohol
D
Alcohol only
correct option: c
Mercury and alcohol are often used in THERMOMETER
Note:Water is never allowed to be used in thermometer because, it doesn’t expand uniformly
Users' Answers & CommentsNote:Water is never allowed to be used in thermometer because, it doesn’t expand uniformly
47
Neutron were discovered by
A
J.J. Thompson
B
James Chadwick
C
Michael faraday
D
Dalton
48
If a projectile has maximum range of 36m, find the speed of projection (Take g = 9.8m/s2)
A
27m/s2
B
2m/s2
C
4m/s2
D
7m/s2
correct option: a
For maximum range (Rmax)
Rmax = U2 ÷ α g where Rmax = 36m, U2 = ?, g = 9.8m/s2
36 = U2 ÷ 2 × 8.8
U2 = 36 × 2 × 9.8m = 705.8
√U = √ 705.6 = 26.5 (squaring both side)
u= 26.5m/s, U = 27m/s (Approx.)
The speed of projection = 27m/s2
Users' Answers & CommentsRmax = U2 ÷ α g where Rmax = 36m, U2 = ?, g = 9.8m/s2
36 = U2 ÷ 2 × 8.8
U2 = 36 × 2 × 9.8m = 705.8
√U = √ 705.6 = 26.5 (squaring both side)
u= 26.5m/s, U = 27m/s (Approx.)
The speed of projection = 27m/s2
49
What is the S.I unit of relative density?
A
kg m-2
B
kg m2
C
kg cm3
D
has no S.I unit
correct option: d
Note: relative density has no S.I unit
∴ Relative density = weight of substance ÷ weight of equal volume of water
RD = w1 ÷ (w1 – w2) (no S. I unit)
Users' Answers & Comments∴ Relative density = weight of substance ÷ weight of equal volume of water
RD = w1 ÷ (w1 – w2) (no S. I unit)
50
For a best result using temperature to achieve an accurate measurement, it is best to use
A
Mercury thermometer
B
gas thermometer
C
clinical thermometer
D
alcohol thermometer
correct option: b
Gas thermometers are considered best for use to achieve an accurate temperature than others, such as liquid in glass thermometers such as mercury, clinical and alcohol thermometer
Users' Answers & Comments