JAMB PHYSICS 2021 POSSIBLE QUESTIONS AND ANSWERS

1. Which of the following radiations cannot be deflected by a magnetic field?
A. Alpha
B. Beta
C. Gamma ✔️
D. None of them

2. Which of the following elements is the best absorber of X-rays?
A. Hydrogen
B. Oxygen
C. Calcium
D. Lead ✔️

O
3. /////////////////
|
|
0.4m |. 0.3m
—|
___________| |
M | N
| P |
|
|
∆
20N
In the above diagram, MN is perpendicular to ON and MP. What is the difference between the moment about N of the force of 20newtons applied along with MP and its moment about O?
A. Zero. ✔️
B. 0.2 N/m
C. 0.4 N/m
D. 0.8 N/m

SOLUTION
Moment about N = 20 × 0.4 =8NHm
Moment about O = 20× 0.4 = 8NHm

Difference = 8 – 8 = 0 (A)

4. Which of the following is not directly associated with direct current (D C ) ?
A. A dry cell
B. A moving coil galvanometer
C. A transformer ✔️
D. A lead accumulator

5. 0—— 3Ω ———–|
| |
| |
2Ω. 2Ω
| |
| |
0——- 4Ω ———- | fig.4

What is the resultant resistance of the circuit ( Fig. 6 ) given above?
RT = 3 + 4 + ½ + ½ = 8Ω (B)

6. Which of the following is a derived unit?
A. Kilogram
B. Metre
C. Kelvin
D. Newton ✔️

7. Number of pulley is ___________
A. Velocity ratio ✔️
B. Mechanical ratio
C. Efficiency
D. Effort

8. The thermometric substance of an absolute thermometer is ?
A. Alcohol
B. Mercury ✔️
C. Helium
D. Platinum

9. An electric cell with normal voltage E has a resistance of 3Ω connected across it. If the voltage falls to 0.6 E , the internal resistance of the cell is
A. 4 Ω
B. 3 Ω
C. 2Ω ✔️
D. 1Ω

SOLUTION
IR = I ( R + r )
I × 3 = 0.6 I ( 3 + r )
3I = 0.6 I ( 3 + r )
r = 2 Ω ( C)

10. A catapult used to hold a stone of mass 500g is extended by 20cm with an applied force F. If the stone leaves with a velocity of 40ms-¹ , the value of F is
A. 4.0 × 10⁴ N
B. 4.0 × 10³ N
C. 2.0 × 10³ N ✔️
D. 4.0 × 10² N

SOLUTION
F = ma
From. V² = u² + 2as
make Note F = m ( v² – u² ) / 2s
0.5 ( 40² – 0² ) / 2 × 0.2
F = 2000N ( C)
__
11. Na + X ——-> 20 |– + 4 |_|
∅ | 2| |e
The above represents. Na + x ———-> F + He
What particle is X in the reaction above ?
A. Beta
B. Gamma
C. Alpha
D. Neutron✔️

SOLUTION
b + 23 = 20 + 4
b = 1
a + 11 = a + 2
a = 0
X = Neutron

12. The process whereby a liquid turns spontaneously into vapor is called
A. Evaporation✔️
B. Relegation
C. Boiling
D. Sublimation

13. A 3 m³ volume of liquid W of density 200kgm-³ is mixed with another liquid L of volume 7m³ and density 150kgm-³. The density of the mixture is
A. 265kgm-³
B. 165kgm-³✔️
C. 100kgm-³
D. 350kgm-³

SOLUTION
Mass of W = density (e) × volume (v)
=. 200 × 3 = 600kg

Mass of L = density (e) × volume (v)
= 150 × 7 = 1050kg
Total Mass = 1650kg
Total volume = 3 + 7 = 10m³

Density of mixture = m / v = 1650 / 10 = 165kg/m³ (B)

14. The bond that forms a semiconductor is
A. Ionic
B. Metallic ✔️
C. Covalent
D. Electrovalent

15. Zener diode is used for
A. Current amplification
B. Power amplification
C. Voltage amplification
D. Energy conversion ✔️

16. When a pure semiconductor is heated, it’s resistance
A. Increases
B. Decreases✔️
C. Remains the same
D. Increases and then decreases