JAMB Physics Past Questions & Answers

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Correct Answer: Option C

Explanation

Shunt resistance is usually given as
R = igrg/(I - ig)
Where R = 0.05Ω
rg = 5Ω
I = 2M
∴ ig = IR/(rg + R)
= (2 x 0.05)/(5 + 0.05)
= 0.10/5.05
= 0.0198A
= 19.8mA
= 20mA

Correct Answer: Option D

Explanation

At constant T, P1 V1 = P2 V2.

Let P1 = P0 and V1 = V0, then solve accordingly.

As pressure is varies inversely as volume according to:

Boyle's law, also referred to as the Boyle–Mariotte law, or Mariotte's law, is an experimental gas law that describes how the pressure of a gas tends to decrease as the volume of the container increases.

As volume is reduced by one-fifth; pressure will increase by five times.

Correct Answer: Option C

Explanation

Total Energy  = Kinetic Energy + Potential Energy

P.E = mgh = 0.1 x 10 x 10= 10 J

K.E = 12$\frac{1}{2}$ MV2${}^2$ =  12$\frac{1}{2}$ x 0.1 x 102${}^2$ = 0.5 x 0.1 x 100 = 5J

T.E = K.E + P.E = 5 + 10 = 15J

Correct Answer: Option C

Explanation

The image of an object placed in front of a plane mirror is always as far behind the mirror as the object is in front of the mirror. Thus when the object is 4m in front of the mirror, the image will be 4m behind the mirror. But when the mirror is moved in towards the man, (that is the man is now 3m from the mirror), the image distance will again decrease by 1m from behind the mirror. Thus the new image position is 3m behind the mirror. Therefore, the distance between the man and his new image is 6m.

Correct Answer: Option A

Explanation

To calculate the power developed in the engine, we need to determine the work done and the time taken.

1. Calculate the final kinetic energy (KE) of the car:

where m=800 kg$m=800 kg$ and v=25 m/s$v=25 m/s$.

2. Calculate the power (P)  developed in the engine using the formula:

where W$W$ is the work done (in this case, equal to the kinetic energy calculated) and t$t$ is the time taken.

Thus, the power developed in the engine is 12500 watts (or 12.5 kW).

Correct Answer: Option C

Explanation

R.D = loss in weight in liquid X loss in weight in water$\frac{}{}$

R.D = (10−7)(10−6)$\frac{(10-7)}{(10-6)}$ = 34

Correct Answer: Option A

Explanation

Heat given off by the copper = MCt
= 2 x 400 x (100 - 0)
Heat absorbed by the ice = ML
= M x 3.3 x 105${}^5$
Heat lost = Heat gained
∴ M x 3.3 x 105${}^5$ = 2 x 400 x 100
∴ M =(2×400×100)3.3×105$\frac{(2\times 400\times 100)}{3.3\times {10}^5}$
= 833$\frac{8}{33}$Kg

Correct Answer: Option C

Explanation

Shunt resistance is usually given as
R = igrg/(I - ig)
Where R = 0.05Ω
rg = 5Ω
I = 2M
∴ ig = IR/(rg + R)
= (2 x 0.05)/(5 + 0.05)
= 0.10/5.05
= 0.0198A
= 19.8mA
= 20mA

Correct Answer: Option B

Explanation

Centripetal Force (Fc${}_c$) = mv2r$\frac{m{v}^2}{r}$

= mω2r$m{\omega }^{2}r$

(Since V = ωr)

F = 0.01 x 1002×0.2${100}^2\times 0.2$

F = 20 N

Correct Answer: Option D

Explanation

A Vernier caliper is an instrument used to measure both the outer and inner diameters of a tube.

Correct Answer: Option C

Explanation

Let the forces be F1, and F2.
F1 = m1 a1 = 3 x 2 = 6N

F2 = m2 a2 = 1 x 9 = 9N

F1 : F2 = 6:9 = 2:3

Thus ratio of forces is 2: 3

Correct Answer: Option C

Explanation

The general wave equation is given by;
y = A Sin(wt - 2πx/Wavelength)
where w = angular velocity

Thus comparing this equation with the equation
y = 0.25 x 10-3 Sin (500t - 0.025x)
That Amplitude = 0.25 x 10-3m
the angular velocity(w) = 500 (the coefficient of t in both equations)
∴ w = 500 rad s-1
= 5.00 x 102rad s-1

Correct Answer: Option D

Explanation

Since all the cells are connected in parallel, the effective e.m.f. is just that of one single cell. Which means e.m.f. = 1.5V

However, the effective internal resistance adds as parallel arrangement given as
1/r = 1/r1 + 1/r2 + 1/r3 + 1/r4
= 1/4 + 1/4 + 1/4 + 1/4
= 1Ω
∴ r = 1Ω

Answer = 1.5V, 1Ω

Correct Answer: Option D

Explanation

Y = stressstrain$\frac{}{}$, but stress = 107${}^7$Nm−2${}^{-2}$ (given).

Strain = elo$\frac{l_o}{}$. = (10.05−10.00)10.00$\frac{(10.05-10.00)}{10.00}$ = 0.005

Thus Y = 1070.005$\frac{{10}^7}{0.005}$ = 2.0 x 109${}^9$Nm−2

Correct Answer: Option B

Explanation

Energy of a particle is given by
E = hf = hV/λ (since V = fxλ)
But in terms of mass M, E = ∆MV²
∴ ∆MV² = hV/λ
∆MV = h/λ
∴ V = h/λ∆M
V = 6.63 x 10^-34/(10^-27 x 10^-8)
V = 6.63 x 10^-34/10^-35
V = 6.63 x 10^-34+35
V = 6.63 x 10
V = 66.3ms^-1

Correct Answer: Option D

Explanation

The maximum current drawn by the cooker is given by;
I = PV$\frac{P}{V}$
∴ I = 3000200$\frac{200}{}$
I = 15A
The fuse rating = I ×$\times$ 125% (the fuse is rated at 125% of the normal operating current)

Hence, the fuse rating = 15A ×$\times$ (125100$\frac{125}{100}$) = 18.75amps

Therefore, the best fuse is 20A.

Correct Answer: Option A

Explanation

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