P2- Electricity Flashcards
Define current
the rate at which electrons flow past a point in a complete electrical circuit
Whats meant by resistance in a circuit
Resistance is a measure of the opposition to the flow of current in an electrical circuit.
Unit: ohms
What is meant by the potential difference of a circuit
Potential difference (or voltage) is a measure of energy, per unit of charge, transferred between two points in a circuit.
What’s the equation for charge flow?
Q = It
Q- charge flow (coulombs, C)
I- current (A)
t- time (s)
Cell diagram
Battery circuit diagram
Switch open and closed circuit symbol
Bulb circuit symbol
Fuse circuit symbol
LED circuit symbol
Resistor circuit symbol
Variable resistor circuit symbol
Ammeter circuit symbol
Voltmeter circuit symbols
Diode circuit symbol
Ldr circuit symbol
Thermistor circuit symbol
What happens to the resistance of a thermistor ad it gets hotter?
Their resistance decreases as the temperature increases.
Series circuits:
Potential difference is _______
Current is _________
Shared
The same everywhere
-resistance adds up
-cell potential difference adds up
Parallel circuits:
Potential difference is_______
Current is________
the same across all components
shared between branches
Graph for resistors in a series circuit
Graph for the number of resistors in a series circuit
Describe an experiment to investigate how adding resistors in series and parallel affects the total resistance of the circuit
What colour is the neutral wire
Blue
The neutral wire completes the circuit
What colour is the live wire ?
Brown
The live wire provides the alternating potential difference between
What colour is the earth wire?
Green and yellow
It is for protecting the wiring and for safety- it stops the appliance casing from becoming live.
What colour is the earth wire?
Green and yellow
It is for protecting the wiring and for safety- it stops the appliance casing from becoming live.
Why can the live wire give you an electric shock?
Since the live wire has a very large potential difference compared to the human body (0V) the live wire can cause shocks. When you touch a live wire, a large potential difference is produced across your body and a current flows through you
The UK mains supply is an ac supply at around _____.
230V
What’s the frequency of the ac mains supply?
50 Hz
What are the functions of step-up and step-down transformers?
A “step-down transformer” is used to step voltage(p.d) down, while a “step-up transformer” is used to step voltage(p.d) up.
Transformers all have two coils , primary, secondary joined with an iron core
What is the national grid?
The National Grid is the system operator of Great Britain’s electricity and gas supply. This includes England, Scotland and Wales. It is the company that manages the network and distribution of electricity and gas that powers all our homes and businesses.
Explain why electricity is transferred by the national grid at a height p.d but low current
The transfer of electrical energy via the grid is very efficient. When currents in a cable are higher, more energy is
dissipated
to the surroundings through heating. As high currents waste more energy than low currents, electrical power is transported around the grid at a high voltage and a low current.
What is the power rating of an appliance?
defines how much energy is being transferred from the mains to power the device
Power=
Potential difference (V) x current (A)
Energy transferred=
Power x time
