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Electric Potential Energy

By Rachel Wampler

Potential Difference

• Change in potential energy due to gravity

  • Force of gravity is conservative

  • W = mgh₀ - mgh_f = PE₀ - PE_f

• Change in potential energy due to electrial force

  • Electrical force is conservative​

  • W = PE₀ - PE_f​

Electrical Potential Evergy vs. Electric Potential

Electric Potential Differnce

Multiple Choice

Electric force moves a charge of 2 x 10^-10 C from point A to point B and does 5 x 10^-6 J of work.

What is the difference in potential energies of A and B? (HINT* PE_A -PE_B)

What is the potential difference between A nd B? (HINT* V_A - V_B)

• -2x10^-10 J

  -4.0x10^-5 V

• -5x10^-6 J

  -25000 V

• 2x10^-10 J

  4.0x10^-5 V

• 5x10^-6 J

  25000 V

Charge

• Electric potential difference and charge signs

  • Positive charge

    • Moves from higher electrical potential toward lower electrical potential

  • Negative charge

    • Moves from lower to higher electrical potential ​

Multiple Choice

Points A, B, and C are evenly spaced on a line. A positive test charge is released from A and accelerates towards B, from B it decelerates, but doesn't stop at C. What happens when a negative charge is released at B?

• Accelerrate towards C

• Accelerate towards A

• Stop at C

• Stop at A

• Even though it is the negative electrons that actually move, tradition says we talk about moving positive charges.

• Positive charges are repelled by the positive terminal

• Moves through a light bulb and energy is converted to heat

• By the time the positive charge reaches the negative ​terminal, it has no potential energy left

Batteries

Volts and energy

Multiple Choice

When lightning strikes, the potential difference can be tens million volts between the cloud and ground. If an electron is at rest and the accelerated from the ground to the cloud, how fast will it be moving when it hits the cloud 0.5 km away? (Ignore relativistic effects)

• 3.00 x 10⁸ m/s

• 1.87 x10⁹ m/s

• 3.51 x10¹⁸ m/s

• 9.11 x10³¹ m/s