Electricity Flashcards
Power (W) equation =
potential difference × current (P = VI)
Current squared x resistance
How do you measure voltz
Using a voltmeter
How do you measure current
Measured using a ammeter (amps)
The amount of energy an appliance transfers depends on what?
how long the appliance is switched on for and the power of the appliance.
When is work done
When charge flows in a circuit
Eqution for energy transfer
power x time (E = Pt)
charge flow x potential difference (E = QV)
How is energy measured
Using a joulmeter or ammeter and voltmeter and stopwatch
What is charge flow (Q) measured in
coulombs, C
What is voltage (V)
Potential difference (energy transfered) measured using a voltmeter
What is the National Grid
The National Grid is a system of cables and transformers linking power stations to consumers. Electrical power is transferred from power stations to consumers using the National Grid.
What are step-up transformers used to do
used to increase the potential difference from the power station to the transmission cables
What are step-down transformers used to do
step-down transformers are used to decrease, to a much lower value, the potential difference for domestic use.
What is resistance
The reduction of flow of electricity measured in ohms
How is potential difference is energy transfer per charge passed
When an electrical charge goes through a change in potential energy, then energy is transfered. Energy supplied to the charge at the power to raise is through a potential. The charge gives up this energy when it falls through potential drop in components eleswhere in the circuit.
Example of electrical appliances designed to transfer energy to components in the circuit when a current flows
Kettles - they transfer electrically from the mains ac to the thermal energy store of the heating element inside the kettle.
Fan - energy is transfer electrically from the battery to the kinetic energy store of the fan’s motor.
How is the National Grid system is an efficient way to transfer energy.
They can predict when the most electicity will be used. Power stations often run at well below their macimum power output and lot of small power stations can start up quickly.
How does the narional grid using high pd insted of current make it more efficient
The problem with a high current is that it gives out lots of thermal energy store to the surrounding by wires heating up. Using more pd decreases the amount of current needed
How is potential difference changed
Use a transformer
How do materials become electically charged
When certain insulating materials are rubbed against each other they become electrically charged.
How do electrons move around materials
Negatively charged electrons are rubbed off one material and on to the other. The material that gains electrons becomes negatively charged. The material that loses electrons is left with an equal positive charge.
What happens when When two electrically charged objects are brought close together
they exert a force on each other. Two objects that carry the same type of charge repel. Two objects that carry different types of charge attract. Attraction and repulsion between two charged objects are examples of non-contact force.
How does too much static energy cause sparks
As electircal charge builds up the potential object between the object and the earth increases. If the pd is large enough, electron can jumo across the gap between the charge objects and earth creating a spark. They can also jump to any earthed conductor
How are materials electrically charged
When electrons transfer leaving a posotiv pe static charge and an eqaul negative charge on the other
What does A charged object create around it
an electric field (The electric field is strongest close to the charged object)
