2001 - JAMB Physics Past Questions and Answers - page 4

The process of energy production in the sun is generally by nuclear fusion of hydrogen nuclei, the reaction of which takes place at a tremendous high temperature of the order of 10⁷K.

H₁ + H₁ 2H

At reasonance in an a.c. circuit, during which the capacitive reactance X_c is equal to the inductive reactance X_l, the phase angle Ø = 0°

The force on a current carrying conductor in a

magnetic field is greatest when the conductor lies perpendicular in the magnetic field

Resonant, frequency in an a.c. circuit is given by F = I/2π√LC

therefore 200 * 10³ = I/2 * π√l * 20 * 10^-12

therefore (2.0 * 10⁵)² = I/4 * π² * L * 20 * 10^-12

THEREFORE L = I/4.0 * 10¹⁰ * 4 * 10 * 20 * 10^-12

(if π² = 10)

= I/16 * 10¹¹ * 2.0 * 10^-11

Therefore L = I/32 H

The magnetic force on a charge is given by

F = qVB Sinθ,

thus the force is proportional to both the magnitude by the charge (q) and the velocity (V)

(i/e F α qV)

The pendulum that will resonate with P is T. being of the same length and therefore of the same frequency.

Since the number of pulleys present is 6, it implies that the velocity ratio VR = 6

= Load/Effort x 1/V.R x 100/1

= ²⁴⁰/₈₀ x ¹/₆ x ¹⁰⁰/₁

= 50%

∴ Efficiency = 50%