Electromagnetism - SS2 Physics Past Questions and Answers - page 2
Two point charges, q1 = +2 μC and q2 = -4 μC, are placed 10 cm apart. What is the electric field at a point located 5 cm from q1 and 5 cm from q2? (Assume vacuum permittivity is ε0 = 8.85 x 10-12 C2/N m2)
Electric field due to q1: E1 = (k x |q1|) / r2
= (9 x 109 N m2/C2 x 2 x 10-6 C) / (0.05 m)2
= 1.8 x 10^6 N/C
Electric field due to q2: E2 = (k x |q2|) / r2
= (9 x 109 N m2/C2 x 4 x 10-6 C) / (0.05 m)2
= 3.6 x 106 N/C
Total electric field at the point: Etotal = E1 + E2 = 1.8 x 106 N/C + 3.6 x 106 N/C = 5.4 x 106
The direction of the electric field will be away from q1 and towards q2.
A parallel plate capacitor with a plate area of 100 cm2 and plate separation of 2 mm is connected to a 12 V battery. What is the electric field between the plates? (Assume vacuum permittivity is ε0 = 8.85 x 10-12 C2/N m2)
The electric field between the plates of a capacitor is given by: E = V / d
E = (12 V) / (0.002 m) = 6 x 103 N/C
However, this electric field is uniformly distributed between the plates, so the electric field magnitude is the same everywhere between the plates.
A point charge of +5 μC is located at the origin. What is the electric potential at a point 2 metres away from the charge? (Assume vacuum permittivity is ε0 = 8.85 x 10-12 C2/N m2)
The electric potential due to a point charge is given by: V = (k x |q|) / r
V = (9 x 109 N m2/C2 x 5 x 10-6 C) / 2 m = 9 x 106 V
The capacitance of a parallel plate capacitor depends on:
The area of the plates.
The distance between the plates.
The dielectric material between the plates.
All of the above.
A capacitor stores energy in the form of:
Electric potential.
Electric current.
Electric field.
Electric resistance.
The capacitance of a capacitor is directly proportional to:
The area of the plates.
The distance between the plates.
The voltage across the capacitor.
The charge is stored on the plates.
The time constant of an RC circuit depends on:
The resistance (R) of the circuit.
The capacitance (C) of the capacitor.
The product of resistance (R) and capacitance (C).
The voltage across the capacitor.
When a dielectric material is inserted between the plates of a capacitor, the capacitance:
Decreases.
Increases.
Remains the same.
Depends on the dielectric constant.
The energy stored in a capacitor is given by the formula:
E = 1/2CV2.
E = 1/2CV.
E = 1/2Q2.
E = 1/2Q.
When two capacitors are connected in series, the total capacitance is:
The sum of the individual capacitances.
The reciprocal of the sum of the reciprocals of the individual capacitances.
The average of the individual capacitances.
The product of the individual capacitances.