WAEC Physics Past Questions & Answers - Page 8

Ferrite magnets are non-conductive aferromagnetic ceramic compounds derived from iron oxides such as Haematite (Fe203) or Magnetite (Fe304) and other metal oxides such as Barium and Strontium.

Ferrite is a polycrystal, sintered material with high electrical resistivity. The high resistance of ferrite makes eddy current losses extremely low at high frequencies.

The relation between period and frequency is that one is the inverse of the other.

By definition:

Frequency = 1/period.

or 

period = 1/frequency → 1/ 10,000

period = 0.0001 or 1.0 x 10\(^{-4}\) s

Two conductors with current flowing in the same direction will attract. 

Sensitivity of a galvanometer increases when number of turns, area of coil and magnetic field increase

The power of a lens is defined as the reciprocal of its focal length in metres:

P = \(\frac{100}{f}\) → 2.5 = \(\frac{100}{f}\)

where P is the power in diopters and f is the focal length in metres.

2.5 * f = 100

f = \(\frac{100}{2.5}\)

f = 40

Where f = \(\frac{r}{2}\)

radius of the curvature[r] = f * 2 → 40 * 2

r = 80cm

beat, in physics, the pulsation caused by the combination of two waves of slightly different frequencies

Objects at a distance greater than two times of the focal length produces a real image, inverted and diminished in size.

→ 2 * 15 = 30cm

: At >30cm this is applicable  

The magnetic meridian is an equivalent imaginary line connecting the magnetic south and north poles and can be taken as the horizontal component of magnetic force lines along the surface of the earth. Therefore, a compass needle will be parallel to the magnetic meridian

VR = 5:1 or 5

Load = 20kg or 200N

MA = \(\frac{200}{E}\)

Efficiency% = \(\frac{MA}{VR} * 100\)

100% = \(\frac{200}{5E} * 100\)

5E = 200

E = 40

Images formed by plane mirrors are virtual, upright, left-right reversed, the same distance from the mirror as the object's distance, and the same size as the object