definitions
Define Current
The flow of charge around a circuit per second
Calculate the resistance in a circuit at 12v with 4A
3Ω
state a safety precaution to take during the resistivity practical
don't touch the wire whilst the circuit is on/ has recently been turned off
describe the I-V graph of a filament lamp
straight line (ohmic) until a certain point at which the line curves
a 12.0V 20W component is connected to a circuit, calculate the current in the component
20W/12V=1.7A
state the resistivity of constantan wire
5x10-7Ω m
Give an example of a non-ohmic component
filament bulb, thermistor
calculate the number of electrons flowing per second, given a circuit has 1A
1A/1s= 1C
1/1.6x10-19 = 6.25x1018
explain why the circuit should only be on for a short period of time when carrying out the resistivity practical
to prevent overheating of the wire
define ohms' law
the electric current through a component is directly proportional to the voltage across the component provided temperature stays constant
A strip of metal has a height of 0.50mm, a width of 1.5cm and a length of 1m, given these dimensions produce a resistance of 50Ω calculate the resistivity of the metal
3.75x10-4Ω m
explain how to practically measure the resistance of an unknown resistor
create a circuit with a cell, an ammeter in series with the resistor and a voltmeter connected in parallel with the resistor, measuring the voltage across the resistor
Explain why diodes are used to covert A.C current into D.C current?
as the provide infinite resistance when current is negative therefore they only allow current through when it is positive
a wire has a diameter of 3.2mm and a length of 2.4m, calculate the resistivity of the wire given it has a resistance of 3Ω
1.01x10-5Ω m
explain why we use Resistance against length for the graph for the resistivity practical
As we are measuring the resistance across the length of wire and we then ise length so that gradient x cross sectional area equals resistivity