electric circuits (required practical) Flashcards
what is current?
the rate of flow of electrical charge.
what is the unit of current?
amps. A
what is voltage? potential difference
the driving force of charge.
what is the unit of voltage?
volts. V
what is resistance?
a measure of how hard it is for current to flow.
what is the unit of resistance?
ohm. Ω
what is charge?
a property of matter e.g. electrons have charge that causes charged objects to experience a force in an electric field. coulombs
what is the unit of charge?
coulombs. C
what is the formula for charge flow?
charge flow coulombs = current amps x time seconds
Q = i x t
how is charge effected by current?
larger current = more charge.
what is the formula for voltage?
volts V = current A x resistance Ω
what is an ohmic conductor?
current and voltage are directly proportional and resistance is constant.
give an example of an ohmic conductor.
a resistor. at a constant temperature
give 2 examples of non ohmic conductors.
- filament lamp. higher temperature from the lamp gives a higher resistance
- diode. current only flows in one direction
how do you find the I-V characteristics of a component (required practical)
- set up a circuit with a 10v power supply connected to a variable resistor connected to a component and a voltmeter in parallel connected to an ammeter.
it looks something like this:
🔋〰v resistor〰component + voltmeter (in parallel) 〰ammeter - vary the variable resistor to change the current. higher resistance = lower current
- take multiple readings of the ammeter and voltmeter to see how the voltage across the component changes with current.
- repeat each reading 3 times to get an average voltage at each current.
- flip the circuit so the direction of the current is reversed.
- take more readings.
- plot a graph of current against voltage.
as R = V÷I you can calculate the resistance at any point
