2025 WAEC PHYSICS: 2025 WAEC GCE Second (2nd) Series PHYSICS ESSAY AND OBJ QUESTIONS AND ANSWERS (6912)

(1a)
Power; = f*d/t = MLT^-² * L/T =ML²T^-³

(1b)
Force; = m*a =MLT^-²

(1c)
Pressure; F/A = MLT^-²/L² =ML^¹T^²

(2)
(i)Boron
(ii)Aluminium
(iii)Gallium

(3a)
(i)Iron
(ii)nickel

(3b)
(i)Magnets are used in magnetic compass, doorbells, refrigerators.

(4)
w = 2π/T
V/R = 2π/T
R/V = T/2π
R = VT/2π
= 8×10³×5×10³/2×3.14
= 6.37×10⁶m

(9ai)
Constant-Volume gas thermometer
(i)Thermometric substance --> Gas
(ii)Physical property --> Change of gas pressure at constant volume with temperature

(9aii)
Thermocouple thermometer
(i) Substance --> Two dissimilar metals
(ii) Property --> Change in electric potential between two metal junctions at different temperature

(9aiii)
Liquid in glasses
(i) Substance --> Mercury or Alcohol
(ii) Property --> Change in volume of liquid with temperature

(9bi)
(i)Smaller in size and can therefore be used to measure temperature nearly at a point
(ii)More sensitive

(9bii)
Radiation

(9ci)
Linear espansivity of a substance is defined as the increase in length per unit length per degree rise in temperature

(9cii)
∆l = L1α∆θ
= 0.3×1.2×10-⁵×50
= 18×10-⁵
= 0.00018m of 0.018cm

(9d)
Heater draws current, I = P/v = 2750/240
= 11.46A
Since this current exceeds the current breaker rated current of 10A, the circuit breakers trios off- line become inactive

(10a)
(i)Long sight
(ii)Short sight

(10bi)
For the man to see objects clearly at 25.0cm from the eye, the image must appear to be at 60.0cm.
Hence ie U = 25cm, V = -60cm
1/f = 1/v + 1/u = 1/-60 + 1/25
1/f = 1/25 - 1/60
1/f = 12-5/300 = 7/300
f = 300/7cm = 42.86
He need a convex lens at focal length 42.86cm(He is long sighted)

(10bii)
Power = 100/f = 100)42.86
= 2.34

(10ci)
Dispersion of light is the phenomenon of light at different wavelengths being separated by retraction by different currents when white light is passed through a glass prism

(1cii)
An echo us a sound heard after the reflection of sound waves from a plane surface

(10di)
V = 2d/t
ie d = Vt/2
= 2800×0.5/2
= 700meters

(10dii)
When white is passed through a triangular glass prism, an elongated coloured pitch of light is obtained on a screen placed behind the prism. The coloured pattern as known as spectrum of white light, and it contains red, orange, yellow, green, blue, indigo and violet

(10diii)
(i)Pitch

(11ai)
(i)Lines of force Start only on positive charges and end only on negative charges.
(ii)Lines of force do not cross each other

(11aii)

(11bi)
The surface density of a conductor is the quantity of say electric charge per unit area flowing through it.

(11bii)
The opposition to the flow of alternating current altered by a capacitor is known as capacitive reaction ie Xc

(11ci)
From ; Xc =1/2πfc, when frequency is increased, Xc drops. Consequently, from I = v/Xc, current increases

(11cii)
Vt = VmSin (wt-90°)
If It = Im Sin wt
Voltage lags by 90°

(11ciii)
Xc = 1/2πfc
:. C = 1/2πfXc = 1/2*3.14*100*500
= 1/314000
= 3.185µF

(11d)
A stator and armature