2020 - JAMB Physics Past Questions and Answers - page 2

Radioactivity is the spontaneous emission of radiation from atomic nuclei. This radiation can consist of alpha, beta, and gamma radiation.

Natural radioactivity is a purely nuclear phenomenon. The nucleus of a radioactive substance is unstable and such an unstable nucleus undergoes spontaneous breakdown (disintegration). The process continues until a stable nucleus is obtained.

The Doppler effect is the change in frequency of a wave in relation to an observer who is moving relative to the wave source. It is named after the Austrian physicist Christian Doppler, who described the phenomenon in 1842. Wikipedia

P = (5 x 50) + (100 x 4)

= 650watts

Energy(kWhr) = 650 x 10-3 x 10

= 6.5 kWhr

1kWhr cost 2 kobo ; 6.5 kWhr will cost 2×6.512×6.51

= 13 kobo

The mass of a proton is equal to that of the hydrogen atom. A hydrogen atom consists of one electron and one proton.

Es = e.m.f. of the secondary coil 

Ep = Np 

Np = e.m.f. of secondary coil 

Ns = number of turns in secondary coil 

Ns = number of turns in primary coil 

$\frac{30}{300}$ = $\frac{x}{100}$ = 300 

X = 3000 

X = 10 volts 

Relative density of solid is given as

$\frac{\text{weight of solid}}{\text{weight of an equal volume of water}}$

= $\frac{4.8}{4.8-2.8}$ 

= $\frac{4.8}{2}$ = 2.4

Relative density of liquid 

=   $\frac{\text{Weight of liquid kerosine}}{\text{Weight of an equal volume of water}}$ 

= $\frac{4.8-3.2}{4.8-2.8}$  = $\frac{1.6}{2}$ = 0.8

= $\frac{\text{Ratio of relative density of solid}}{\text{Relative density of Kerosine}}$ 

= $\frac{\text{density of solid}}{\text{density of Kerosine}}$

= $\frac{2.4}{0.8}$ 

= 3

(A) R${}_T$ = 2 + 3 + 6 = 11$\mathrm{\Omega }$ 

(B) R${}_T$ = $\frac{3\times 3}{2+3}$  = 1.2$\mathrm{\Omega }$ 

(C) R${}_T$ = $\frac{3\times 2\times 6}{(2\times 3)+(2\times 6)+(3\times 6)}$ 

= 1$\mathrm{\Omega }$ 

(D) R${}_T$ = 3 + $\frac{2\times 6}{2+6}$ 

= 4.5 $\mathrm{\Omega }$