Pakistan MCQs

For two parallel resistors, R=R1R2/(R1+R2).
R=18/9 = 2 Ω.

Magnetic force is qvB sinθ in magnitude.
It changes direction of motion but does no work on the charge.

Equal parallel resistors have equivalent R/n.
6/3 = 2 Ω.

Faraday's law links induced emf to the rate of magnetic-flux change.
Relative motion or changing current can produce induction.

Electrical power is P=VI.
P=240×5 = 1200 W.

Lenz's law gives the direction of induced current.
It reflects conservation of energy.

Energy is E=Pt.
E=100×60 = 6000 J.

For a uniform field, flux is BA cosθ.
Its SI unit is the weber.

Use P=I²R.
P=3²×4 = 36 W.

AC reverses direction with time.
Mains electricity is commonly sinusoidal alternating current.

Capacitance is C=Q/V.
C=20 μC/10 V = 2 μF.

Transformers use changing magnetic flux in coupled coils.
They ideally conserve power while changing voltage and current.