Electrostatics

Two point charges of 2 microcoulomb and 3 microcoulomb are 3 m apart in air. The force between them is about: (k = 9 x 10⁹ N m²/C²)

• 1 6 x 10⁻³ N
• 2 1.8 x 10⁻² N
• 3 2 x 10⁻³ N
• 4 6 x 10⁻⁶ N

The electric field inside a charged conductor in equilibrium is:

• 1 Infinite
• 2 Maximum
• 3 Equal to the surface field
• 4 Zero

The SI unit of electric field is:

• 1 C/N
• 2 J/C only
• 3 N/C
• 4 N m

Two plates of a capacitor are 2 mm apart with a potential difference of 100 V. The field between them is:

• 1 5 x 10⁴ V/m
• 2 2 x 10⁵ V/m
• 3 200 V/m
• 4 5 x 10² V/m

Capacitors in parallel have a combined capacitance equal to:

• 1 The reciprocal of the sum
• 2 The product
• 3 The smallest one
• 4 The sum of the capacitances

Gauss's law relates the electric flux through a closed surface to the:

• 1 Charge enclosed
• 2 Outside charge
• 3 Surface area only
• 4 Mass

The energy stored in a capacitor of capacitance C charged to voltage V is:

• 1 1/2 C V
• 2 C V
• 3 1/2 C V²
• 4 C V²

A dielectric placed between capacitor plates:

• 1 Does not change it
• 2 Decreases the capacitance
• 3 Increases the capacitance
• 4 Removes the charge

The electric potential at a point is the work done per unit charge in bringing a:

• 1 Positive test charge from infinity
• 2 Negative charge to the earth
• 3 Mass from the ground
• 4 Neutron from infinity