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?
the size of the current.
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?
in an ohmic conductor the current is directly proportional if one increases so does the other to the voltage and the resistance is always the same.
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 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