current, potential difference and resistance Flashcards
What is electric current ?
It is a flow of electrical charge
What is current measured in ?
Amperes
What is charge measured in ?
Coulombs
What is potential difference ?
The difference in the amount of energy that charge carriers between two points in a circuit
What is the unit for potential difference ?
Measured in volts
What is resistance ?
Resistance is a measure of the opposition to current flow in an electrical circuit.
What is the unit for resistance ?
Measured in ohm
What is the relationship between current, potential difference and resistance?
The current flowing through is directly proportional to to the potential difference across it
What is the equation for potential difference ?
Potential difference (volts) = current (amps) x by resistance (Ω - ohms)
V = I X R
Explain an Ohmic conductor ?
Current is directly proportional to potential difference
You get a straight line
Explain a filament lamp ?
Temperature increases as current increases
Resistance increases
Harder for current to flow
Graph gets less steep
Explain a diode ?
Current only flows in 1 direction
Has a high resistance in the reverse direction
What does LDR stand for ?
Light dependent resistor
Facts about LDR
Resistance of LDR changes as intensity of light changes
Bright light = low resistance
Darkness = high resistance
Advantages of LDR
Automatic night lights
burglar detectors
What is a thermistor ?
A temperature dependent resistor
In hot conditions the resistance drops
In cool conditions the resistance goes up
Used in car engines
Thermostats turn heating on when its cool and off when its warm
What is the difference between series and parallel circuit ?`
If there are no branches then it’s a series circuit. If there are branches it’s a parallel circuit.
How do you get from
kilogram to gram
centimetres to metres
Kilowatt to watt
Amps to milliamps
kg - g = x 1000
cm - m = ÷ 100
kilowatt - watt = x 1000
amps-milliamps = x1000
Physics units
Quantity Unit Symbol
—————————————————————————-
Mass Kilogram kg
Length metre m
Time seconds s
Force Newton N
Energy Joules J
Temperature degree Celsius °C
Area square metre m2
Volume cubic metre m3
Power watt W
Frequency hertz Hz
Potential Difference volt V
Current ampere A
Resistance ohms Ω
Charge coulombs C
