Electric Force, Field, and Potential

Electric Force

100

When using Coulomb's Law (the electric force equation), what does a positive value indicate?

Charges Repel!

200

Two charges are placed at a distance r away and experience a force of 20 N. If the distance between the charges is doubled, what is the new force?

5 N. 

300

A 2 µC charge is located 2 cm to the right and 30 degrees above a 4 µC charge. What is the magnitude and direction of the x-component of the force on the 2 µC charge.

156 N right

400

Three particles of charge 17 µC are located at the corners of an equilateral triangle of side length 15 cm. What is the magnitude of the net force on any one of the charges?

200 N

500

A charged particle is 2 cm from a 3 µC charge. To what distance should the particle be moved to feel a force that is 1/9th the original force?

6 cm. 

Electric Field

100

The electric field is defined as the force per what?

charge!!!

200

Electric field lines always point toward what type of charge?

Negative charges

300

Determine the magnitude and direction of the electric force on a proton in a uniform electric field of strength 2460 N/C east. 

3.94x10^-16 East

400

You are given two unknown point charges, Q₁ and Q₂. At a point on the line joining them, one-third of the way from Q₁ to Q₂, the electric field is zero. What is the ratio of Q₁ to Q₂?

1/4

500

What electric field strength is enough to levitate a proton? (m = 1.67x10^-27 kg)

1.02x10^-7 N/C

Electric Potential

100

A constant electric field of strength 10 N/C is held between two parallel plates a distance of 3 cm apart. What is the potential difference between these plates?

30 V.

200

What kinetic energy in electron volts will a charge with a magnitude 8x greater than an electron gain when accelerated through a potential difference of 50V?

400 eV

300

What is the value of the electric potential 2 cm from a proton?

7.2 x 10^-8 V. 

400

How much energy is required two electrons 10^-9 m apart?

2.3x10^-19 J

500

A proton is placed 2 cm from a charge of 2µC and is allowed to accelerate away. How fast is the proton traveling at 4 cm from the charge?

9.3 x 10⁶ m/s

Electric Charge

100

What is the sign of the charge on an electron

Negative

200

A total charge of -Q is removed from a conductive sphere. What is the charge of the sphere now?

+Q

300

A conductive sphere of charge 2Q comes in contact with a conductive object of charge -Q. What is the charge on both objects after contact is made?

+1/2 Q

(Net charge of +Q distributed between the 2 objects.)

400

What gaussian surface (shape) will you use to find the electric field from a line of charge when using gauss' law?

Cylinder!

500

A sphere encloses a positive charge of 10 µC. What is the electric flux through this surface?

1.13x10⁶ Nm²/C

Capacitors

100

The amount of charge a capacitor stores per volt is what property of a capacitor?

The capacitance!

200

What is the unit of capacitance?

The Farad

300

How much energy is stored in a 4 µF capacitor when connected to a 12 V battery?

2.88x10^-4 J

400

A capacitor has a capacitance of 10 µF with only air between the plates. What charge is stored on this capacitor if a dielectric with a dielectric constant of 3 is placed between the plates of the capacitor and a voltage of 20 V is applied?

6 x 10^-4 C

500

The electric field between the plates of a paper (k=3.75) capacitor is 8.24 x 10⁴ V/m. The plates are 1.95 mm apart, and the charge on each is 0.675 µC. Determine the capacitance of this capacitor and the area of each plate.

4.2x10^-9 F, 0.247m²