2009 - JAMB Physics Past Questions and Answers - page 1

The leaves collapse as the position charges on the rod neutralize the negative charges on the electroscope

Primary colours are red, blue and green
∴ orange is a secondary colour

The leaves collapse as the positive charges on the rod neutralize the negative charges on the electroscope.

Energy generated = power X time = 60w x 1h = 60 x 60 x 60 ws = 216000j = 2.16 x 10⁵J

Number of tunes, n = 500
Area, A = 0.2m + 0.2m = 0.4m²
change of flux density A B
= 1.0 - 0.4 = 0.6T
Tune, t = 5 su
Induced emf, ξ = (AB AN)/AT
(0.6 x 0. 04 x 500)/5
= 2.4v

Canorous cells can be destroyed with a high penetrating radiation which is x - rays

Half-life, T (1)/2 = (0.693)/∆ = (0.693)/ 0.231 = 3.0sec

The number of disintegration,∆N in time interval At, is given by
- ∆N = N∆t
Where N is the number of atoms present at the time t
But ^ = (0.693)/T
∴ ∆N = (0.693)/1(1)/2 N∆t = (0.693 x 10)^{20 x 10}/20 = 3.47 x 10¹⁸

Thermionic emission is ejection of electron from a metal surface as a result of heating.

Metals are good conductors due to the presence of free electrons