PHY 102 TEST PAPER 2025/2026 QUESTIONS AND
SOLUTIONS MARKED A+
✔✔Resistors in Parallel - ✔✔1/Req = 1/R1+1/R2+1/R3+...
Connected across same potential difference/one current goes different paths
✔✔Capacitors in Parallel - ✔✔Ceq = C1+C2+C3+...
unit = farad, F
✔✔Capacitors in Series - ✔✔1/Ceq = 1/C1+1/C2+1/C3+...
✔✔RC Circuit - ✔✔Charge: q(t) = Ce(1-e^(-t/T), T = RC
Current: I(t) = (e/R)e^(-t/T)
✔✔Magnetic field direction - ✔✔B is the direction of the north-seeking arrow
✔✔Magnetic force - ✔✔F = qvBsintheta
unit = newton, N
✔✔Magnetic field magnitude - ✔✔B = F/qvsintheta
unit = Tesla, T
✔✔Right hand rule - ✔✔Thumb in direction of force
Fingers in direction of speed
Magnetic field found through direction of fingers
For negative charge reverse direction of force
✔✔Radius of circular orbit - ✔✔r = mv/qB
✔✔Magnetic force on current carrying wire - ✔✔F = ILBsintheta
unit = newton, N
✔✔Torque on rectangular loop - ✔✔torque = IABsintheta
unit = Nm
Zero net force
✔✔Torque on general loop - ✔✔torque = NIABsintheta
unit = Nm
✔✔Current carrying wire right hand rule - ✔✔Thumb along wire in direction of current
Fingers curl in direction of magnetic field
✔✔Magnetic field for wire - ✔✔B = mu0I/2pir
, ✔✔Force on a wire from another wire - ✔✔F = mu0I1I2L/2pid
✔✔Magnetic field from circular loop - ✔✔B = Nmu0I/2R
✔✔Magnetic field of a solenoid - ✔✔B = mu0(N/L)I = mu0nI
unit = tesla, T
Very small outside solenoid
✔✔Constant magnetic field - ✔✔Zero induced emf
✔✔Magnetic flux - ✔✔flux = BAcostheta
unit = Tm^2, wb
✔✔Faraday's Law of Induction - ✔✔e = -N(delta flux/delta t)
Absolute value to find magnitude
✔✔Lenz's Law - ✔✔An induced current always flows in a direction that opposes the
change that caused it.
✔✔Induced emf in rotating coil - ✔✔e = NBAwsinwt
w = angular frequency
w = 2pif
✔✔Inductance - ✔✔L = delta I/delta t
unit = V s/A, henry, H
✔✔Inductance of a solenoid - ✔✔L = mu0(N^2/l)A = mu0n^2Al
✔✔Ideal inductor - ✔✔Switch closed for a long time --> I = e/R
✔✔RL circuit - ✔✔I = (e/R)(1-e^(-t/torque)
torque = L/R
✔✔Energy stored in inductor (L) that carries current (I) - ✔✔U = 1/2LI^2
✔✔Energy stored per volume in a magnetic field - ✔✔uB = B^2/2mu0
✔✔Direction of propagation for electromagnetic waves - ✔✔Fingers in direction of E
Curl fingers toward B
✔✔Types of electromagnetic waves - ✔✔Radio/TV, Microwave, Infrared, Visible,
Ultraviolet, X-rays, Gamma rays
Increasing frequency
Decreasing wavelength
SOLUTIONS MARKED A+
✔✔Resistors in Parallel - ✔✔1/Req = 1/R1+1/R2+1/R3+...
Connected across same potential difference/one current goes different paths
✔✔Capacitors in Parallel - ✔✔Ceq = C1+C2+C3+...
unit = farad, F
✔✔Capacitors in Series - ✔✔1/Ceq = 1/C1+1/C2+1/C3+...
✔✔RC Circuit - ✔✔Charge: q(t) = Ce(1-e^(-t/T), T = RC
Current: I(t) = (e/R)e^(-t/T)
✔✔Magnetic field direction - ✔✔B is the direction of the north-seeking arrow
✔✔Magnetic force - ✔✔F = qvBsintheta
unit = newton, N
✔✔Magnetic field magnitude - ✔✔B = F/qvsintheta
unit = Tesla, T
✔✔Right hand rule - ✔✔Thumb in direction of force
Fingers in direction of speed
Magnetic field found through direction of fingers
For negative charge reverse direction of force
✔✔Radius of circular orbit - ✔✔r = mv/qB
✔✔Magnetic force on current carrying wire - ✔✔F = ILBsintheta
unit = newton, N
✔✔Torque on rectangular loop - ✔✔torque = IABsintheta
unit = Nm
Zero net force
✔✔Torque on general loop - ✔✔torque = NIABsintheta
unit = Nm
✔✔Current carrying wire right hand rule - ✔✔Thumb along wire in direction of current
Fingers curl in direction of magnetic field
✔✔Magnetic field for wire - ✔✔B = mu0I/2pir
, ✔✔Force on a wire from another wire - ✔✔F = mu0I1I2L/2pid
✔✔Magnetic field from circular loop - ✔✔B = Nmu0I/2R
✔✔Magnetic field of a solenoid - ✔✔B = mu0(N/L)I = mu0nI
unit = tesla, T
Very small outside solenoid
✔✔Constant magnetic field - ✔✔Zero induced emf
✔✔Magnetic flux - ✔✔flux = BAcostheta
unit = Tm^2, wb
✔✔Faraday's Law of Induction - ✔✔e = -N(delta flux/delta t)
Absolute value to find magnitude
✔✔Lenz's Law - ✔✔An induced current always flows in a direction that opposes the
change that caused it.
✔✔Induced emf in rotating coil - ✔✔e = NBAwsinwt
w = angular frequency
w = 2pif
✔✔Inductance - ✔✔L = delta I/delta t
unit = V s/A, henry, H
✔✔Inductance of a solenoid - ✔✔L = mu0(N^2/l)A = mu0n^2Al
✔✔Ideal inductor - ✔✔Switch closed for a long time --> I = e/R
✔✔RL circuit - ✔✔I = (e/R)(1-e^(-t/torque)
torque = L/R
✔✔Energy stored in inductor (L) that carries current (I) - ✔✔U = 1/2LI^2
✔✔Energy stored per volume in a magnetic field - ✔✔uB = B^2/2mu0
✔✔Direction of propagation for electromagnetic waves - ✔✔Fingers in direction of E
Curl fingers toward B
✔✔Types of electromagnetic waves - ✔✔Radio/TV, Microwave, Infrared, Visible,
Ultraviolet, X-rays, Gamma rays
Increasing frequency
Decreasing wavelength
