ECAT Physics MCQs

After each half-life, the number of undecayed nuclei halves.
The process is statistical and exponential.

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.

Use F=kq1q2/r² with charges in coulombs.
F=9×10^9×2×10^-6×3×10^-6 = 0.054 N.

Coulomb force varies inversely with distance squared.
Tripling distance multiplies force by 1/3² = 1/9.

Electric field is force per unit charge.
E=20/4 = 5 N/C.

Electrical work is W=QV.
W=2×12 = 24 J.