Electricity Flashcards
What is a current
A measure of the flow of electrons around a circuit (amps)
What is Potential difference
It is the force driving the flow of electrons (voltage)
What is a circuit
Closed loop
What is Resitance
Everything that resists or opposes the flow of electrons
Which way does current flow in a circuit
From positive to negative
Potential difference/Voltage (V) =
Current (A) x Resistance (Ohms)
Why does a filament lamps Voltage and current graph bend
High temp = High resistance
What is a diode
Has very high resistance in one direction and very little in another
Example of directly proportional in electricity
When resistance stays the same, Voltage is directly Proportional to Current
What is always the same in a series circuit
Current is always the same
What is a series circuit
A electrical circuit with only one loop
What is a parallel circuit
a electrical circuit with more than one loop
What happens when a single part stops working or breaks in a series circuit
it will stop working
In a series circuit, what happens with the voltage/potential difference
It is shared with all components, (So if two of the same lamps and battery voltage is 12V, both will have 6V)
In a parallel circuit what happens to the PD/voltage
All components get all of the voltage
In a parallel circuit what happens to the current
shared between components (12A = 5A + 7A)
In a parallel circuit what happens to the Resistance
More components in the circuit the less the resistance (More choices or pathway)
What is AC
Alternating current is when we use an alternating voltage which swaps back and forward. 230/240 V and 50Hz
What is DC
Stays either + or -, Used for phones or calculators
What are Oscilloscopes
Make potential difference/time graphs
What do cells provide electrons
energy
What store of energy do cells have
Chemical potential energy
What is electro-magnetism
When an electrical current forms its own magnetic field
What are 4 ways we can increase the strength of an electro magnet
More current
More turns in coil
Less coil with same turns
Iron core
Why can’t the national grid have a high current, and what does it do instead?
High current would cause the temperature to increase to high amounts, meaning that it would heat up, instead we increase the voltage to large amounts
How does the national grid work
Power stations produce energy through fission or other, this energy goes through step up transformers which increases the voltage, this is then transported to houses where step down transformers decrease the voltage so that the electricity can be used.
How does a fuse work
made of thin wire
* fuse connected between live pin and wire to kettle
* temperature of wire depends on current in it
* when the current is (very) large, the temperature
of the wire increases beyond melting point of wire
* fuse (wire) breaks
* disconnects mains supply to kettle
* prevents damage to house wiring
* (now) there is no possibility of live wire in kettle
being at mains voltage
How does the earth wire work
earth wire connected to metal case
* metal case is a conductor
* (when live touches case) resistance between live
and earth is very low
* (very) large current to earth through (low
resistance) earth wire
* case is kept at same potential as earth
* so cannot get a shock if (earthed) person touches
metal case
