Unit 1 Definitions

Question 1

Define emf

Answer 1

The electrical energy transferred per unit charge

Question 2

Define resitivity

Answer 2

The resistance multiplied by the cross sectional area of a material divided by its length (can show equation with ALL components identified in words)

Question 3

Define internal resistance

Answer 3

Loss of potential difference per unit current in the source (when current passes through it). No current flow, no lost volts.

Question 4

Define directly proportional relationship

Answer 4

As y increases x increases by the same factor (double x, y doubles and so on). A straight lined graph passing through the origin (0,0)

Question 5

Define current

Answer 5

Flow of charge / electrons

Question 6

Define power

Answer 6

The rate of transfer/dissipation of energy (Joule per second or Watt)

Question 7

Define rms pd/current

Answer 7

The value of direct current/pd that would give the same heating effect as the alternating current/pd in the same resistor.

The rms VALUE is peak divided by square root 2.

Question 8

Define Ohm’s Law

Answer 8

The pd across a material is proportional to the current through it. Provided the physical conditions (temperature) do not change.

Question 9

Define Resistance

Answer 9

The pd across a component divided by the current flowing through it.
It is caused by repeated collisions between charge carriers in the material with each other and with the fixed ions.

Question 10

Define potential difference

Answer 10

The work done (or energy transferred) per unit charge

Question 11

What is mean power?

Answer 11

Half the peak power. 1/2peak current squared x resistance.