Electrostatics and capacitors

What is the force between two point charges of 1 microcoulomb each, placed 1 m apart in air? (k = 9 x 10^9 N m2/C2)

• 1 9 x 10^-3 N
• 2 9 N
• 3 9 x 10^-6 N
• 4 0.9 N

What is the electric potential at 3 m from a point charge of 1 microcoulomb? (k = 9 x 10^9 N m2/C2)

• 1 300 V
• 2 3000 V
• 3 9000 V
• 4 27000 V

If the separation between the plates of a parallel plate capacitor is halved, its capacitance:

• 1 Halves
• 2 Doubles
• 3 Stays the same
• 4 Becomes four times as large

Inserting a dielectric between the plates of a capacitor (battery disconnected or connected) makes its capacitance:

• 1 Decrease
• 2 Increase
• 3 Zero
• 4 Unchanged

A 3 microfarad and a 6 microfarad capacitor are connected in parallel. What is the total capacitance?

• 1 2 microfarad
• 2 4.5 microfarad
• 3 9 microfarad
• 4 18 microfarad

One volt is equal to one:

• 1 Joule per coulomb
• 2 Coulomb per joule
• 3 Ampere per ohm
• 4 Newton per metre

A potential difference of 100 V is applied across two plates 0.02 m apart. What is the electric field between them?

• 1 2 V/m
• 2 500 V/m
• 3 2000 V/m
• 4 5000 V/m