chapter 9: electric circuits

Ohm's Law

The current through an ohmic conductor is directly proportional to the p.d. across it (provided physical conditions remain constant)

Ohmic conductor

A conductor whose resistance remains constant (follows Ohm's Law) when physical conditions do not change

Resistance

A measure of how difficult it is for current to flow through a material (R = V/I)

Resistivity

A measure of how difficult it is for charge to flow through a specific material (independent of shape)

Internal resistance

The resistance within a power source itself which causes energy to be dissipated inside the source

Lost volts

The difference between a source's e.m.f. and its terminal p.d. caused by the p.d. across the internal resistance

Terminal p.d.

The potential difference across the terminals of a power source when it is supplying current

Potential divider

A circuit with two resistors in series that splits the input p.d. in the ratio of their resistances

Filament lamp

A lamp where resistance increases with temperature because ions vibrate more making it harder for charge carriers to pass

Light-dependent resistor (LDR)

A semiconductor whose resistance decreases as light intensity increases

Thermistor

A semiconductor whose resistance decreases as temperature increases