1995 - JAMB Physics Past Questions and Answers - page 4

\(\frac{V_1}{V_2}\) = \(\frac{I_1R_1}{I_2R_2}\)

\(\frac{I_1}{I_2}\)V₂ = 3V₁ and R₁ = 2R₂

\(\frac{V_1}{3V_1}\) = \(\frac{I_1 \times\ 2R_2}{I_2\times R_2}\)

\(\frac{I_1}{I_2}\) = \(\frac{6}{1}\)

I = \(\frac{E.m.f}{R + r}\)

= \(\frac{12}{1 + 0.5}\)

I = 8A

Heat energy = Elect. energy


heat energy= I²RT

= 2 X 2 X 50 X 200

= 40000J

to convert to kJ, divide J by 1000

hence, \(\frac{40000}{1000}\) = 40kJ

P = \(\frac{V^2}{R}\)

= \(\frac{20 \times 20}{100}\)

= 4W

\(\frac{V_s}{V_p}\) = \(\frac{N_s}{N_p}\) = \(\frac{I_p}{I_s}\)

\(\frac{100}{400}\) = \(\frac{V_S}{12}\)

V = 3V

Work function = 5 - 2

= 3eV