Current, Potential Difference and Resistance

what is electrical current?

the rate of flow of electrical charge

what is the equation for current

charge flow = current x time

• Q = I t

what is current measured in?

Amperes/Amps (A)

What is charge flow measured in?

Coulombs (C)

what is potential difference?

a measure of energy, per unit of charge, transferred between two points in a circuit

what is the equation for potential difference?

potential difference = current x resistance

• V= I R

what is potential difference measured in?

Volts (V)

What is resistance measured in?

Ohms (Ω)

rp 3

what is the resistance of an ohmic conductor?

• directly proportional to the potential difference across a resistor

  • constant as the current changes

what is the resistance of a filament lamp

the resistance of a filament lamp increases as the temperature of the filament increases

what is the resistance of a diode?

• current only flows in one direction

• very high resistance in the reverse direction

how does resistance change in a thermistor?

the resistance of a thermistor decreases as the temperature increases

what is an application of thermistors in everyday life?

thermostats

how does resistance change in an LDR?

the resistance of a LDR decreases as light intensity increases

what is an application of LDRs in everyday life?

automatic lights (turn on when it gets dark)

rp 4 - I-V graphs