P2 electricity Flashcards
what are Kirchhoff’s laws
1.if a current splits off into several others those others must add up to make whats been split eg:10 is split into 6 and 4
2.The sum of voltages of each component on a loop of a circuit equals the voltage of the cell
What is the equation for voltage (Ohm’s law)
V=IR or Voltage=current * resistance
What does the voltmeter do
measures the potential difference between two point of a circuit
what does an ammeter do
measures the current through a point on a circuit
what does a resistor do
resists the flow of current through a point, all components that use power have resistance (e.g. bulb)
whats a variable resistor, why are they useful?
a resistor where you can change what the resistance is
They allow you to alter the current through a circuit
what’s current measured in
amps
what’s voltage/ potential difference measured in
volts
what’s resistance measured in
ohms
what is charge measured in
colombs
what is a light resistant diode
a resistor that alters depending on light
what is the equation for charge flow
current * time
a straight line through a voltage current graph means what?
resistance is constant
what is an ohmic resistor
a resistor in which the current is directly proportional to the voltage at a constant temperature
-this means resistance remains the same as current changes
name 2 differences between series and parallel circuits
-total voltage in series circuit is shared through components while in parallel the total voyage inputted is the same at every component
-same current through each component but in parallel total current from the power supply is the sum of all the currents from the components
equation for power
P=IV
name 2 features of direct current
-has a voltage that is always positive or negative (constant direction)
-type of current supplied by batteries
name 2 features of alternating current
-voltage changes from positive to negative (alternating direction) with some frequency
-type of current in mains electricity
what is mains voltage and frequency in the Uk
230V and 50Hz
what colours are the live, earth and neutral wires
brown, yellow and green, blue
what does the earth wire do
it acts as a safety wire which stops the exterior of the appliance to become live
how does an electric shock work
-live wire between wall and switch is still at an alternating potential
-needs path for electricity to flow through
-if someone touches the wire it creates a potential difference from wire to the earth and flows through you into the ground
what is the equation for efficiency
useful energy transfer/total energy transfer
what is the equation for energy transferred
power * time
