Ch. 17 Electric Potential

Potential energy can only be defined for what type of force?

only for a conservative force

How are potential and kinetic energy connect in terms of change?

when there is a change in potential energy there is a negative change in kinetic energy

As a (+) particle moves to the right, what happens to the kinetic, potential, and work

Kinetic energy = increases

Potential Energy = decreases

work = done on particle by electric field (so increases)

Would a charge of 2q have more electric potential energy than a charge of q?

Yes, but same potential energy

Can work be related to force and charge?

Yes, W = Fd = qEd

• if E is uniform

What is breakdown voltage?

the electric field will become strong enough to initiate a current

• ex: lightning or spark

• “if E is too big, you will get a spark”

What are equipotential lines?

• lines indicating constant elevation/electric potential

• lines are closed

• Conductor = entire V and Surface are at same potential

• Lines are perpendicular to electric field

How do equipotential lines look like in between 2 parallel plates?

• straight lines (from + to -)

How do equipotential lines look like in between 2 point charges?

• the lines of equal potential are curves

• still perpendicular to E

true or false: 1V would have 1 eV

true (must always be converted to Joules)

If two points are at the same electric potential, does it mean no work is done in moving a test charge from point A to point B? How does this relate to force?

No work is done!

• if you are moving at the same PE, then the formula is equal

• no PE means no KE

• Forces are equal and opposite to be 0

What is an electric dipole?

Two charges equal in magnitude but opposite in sign which are close together

• total charge is zero but still some effect

What are electric dipole moments?

electric dipole moments are associated with molecules and SMALL

What is capacitance?

• store charge (energy) on conducting plates (between 2 plates)

• “condensor”

In regards to capacitance, how is V viewed as?

V = potential difference (drop the change)

What is a charge on a capacitor related to?

• related to capacitance and voltage

  • does NOT depend on Q/V

  • DOES depend on physical characteristics

If capacitance is large, where does the potential lie?

it is low

What are dielectrics?

• material (insulator) between plates of a capacitor increasing the capacitance

  • helps separate plates (get close but not too close)

  • breakdown less easily

    • more charge can be stored

True or False: energy stored is equal to the work done to charge the capacitor

true

• work done to move charge from plate to plate

• use average voltage

Where is energy stored?

• stored in electric field

T/F: Analog signal voltages are constant

False:

• analog signal voltages vary continuously

True or False: digital signals use binary #’s to represent numerical values (jump between values)

How is an analog signal converted to a digital signal?

• must be sampled

What is one advantage of digital signals

they are less prone to interference (noise)

What is a cathode ray tube used for? in regard to television?

• to emit electrons

• they brighten the screen for a brief period when directed to a screen

How is electric charge used to measure the heart?

• electrocardiogram detects heart defects by measuring changes in potential on the surface of the heart