Investigating Resistance P1 Flashcards
What does an ammeter do?
measure current in amps flowing through test wire
Must be placed in series with investigate
What does a voltmeter do?
Measure the pd over a test wire in volts.
Placed in parallel around what you are investigating
What is the method in investigating resistance?
- attach crocodile clip to wire at 0cm
- attach second crocodile clip at length that will vary start at 10 cm
- close switch and record current through wire and pd across it
- open switch move the crocodile clip close switch and record new length current and pd
- repeat at different lengths
- use measurements to calculate resistance R = V / I
- plot graph and add line of best fit
- should be straight like through origin as directly proportional to length
- if doesn’t go to origin it could be systematic error as not at 0cm
define the term I-V characteristics
refers to a graph which shows how the current flowing through a component changes as the potential difference across it increases.
V = I R
what are linear components?
has a I-V characteristic that is a straight line
what is the independent, dependent and control variables
independent - length of the wire
dependent - resistance
control - temperature of wire(turn of between readings, leave to cool), potential difference of battery, type of wire, diameter of wire
what is a non-linear component?
have a curved I-V characteristic
What is the method to investigate a components I-V characteristic?
- set up test circuit with ammeter, variable resistor, component, voltmeter in parallel and battery
- begin to vary variable resistor. This alters current in circuit and the pd across the component.
- Take several readings and work out resistance.
- repeat to get average
- swap over the wires connected to cell of the direction of current is reversed
- plot graph of current against voltage for the component
