Topic 5.1: Electric Potential Difference, Current and Resistance

Question 1

Define electric potential

Answer 1

o Electric Potential: the potential energy that each coulomb of positive charge would have if placed at that point in the field

Question 2

Define electric potential difference

Answer 2

Electric Potential Difference (V): The work done per unit charge moving a positive test charge between two points in a circuit. V=W/Q measured in volts.

Question 3

Define potential difference

Answer 3

 the potential difference or p.d. is the energy transferred when one coulomb of charge passes from one point to the other point

Question 4

Where does a potential difference act?

Answer 4

o A potential difference acts across a component

Question 5

Define volt

Answer 5

o Volt (1V): Unit of potential difference. One joule of electric potential energy is transferred to other forms when one coulomb flows between two points.

Question 6

• 5.1.2: Determine the change in potential energy when a charge moves between two points at different potentials

Answer 6

o Energy transferred is equal to the amount of electric potential energy gained or to the amount of kinetic energy gained

Question 7

Define electronvolt

Answer 7

o Electronvolt: Unit of energy. The energy required to move one electron through a PD of one volt. W (eV) = q (electron charges) x V (volts)
o 1 eV = 1.6 x 10-19 J

Question 8

Define electric current

Answer 8

o Electric Current (I): The rate of flow of charge. Unit is the ampere. Conventional current flows from positive to negative
 electrons flow from negative to positive
 measured using an ammeter
• the ammeter is placed in the circuit so that the electrons pass through it
o therefore placed in a series circuit

Question 9

Define current

Answer 9

o The current is defined in terms of the force per unit length between parallel current-carrying conductors

Question 10

Define resistance

Answer 10

o Resistance (R): The ratio of potential difference across a conductor to current through the conductor.

Question 11

Define the ohm

Answer 11

o The Ohm (1Ω): 1Ω = 1V/A

Question 12

State Ohm’s Law

Answer 12

o Ohm’s Law: The current through a conductor is directly proportional to the voltage across its ends if the temperature and other conditions are constant.

Question 13

Define non-ohmic conductor

Answer 13

o Non-Ohmic Conductor: A conductor which does not obey Ohm’s Law so V is not proportional to I.

Question 14

Define power

Answer 14

o Power (P): The rate of converting energy. Unit is watt (W) = 1J/S