electricity Flashcards
(32 cards)
what is charge? what are the units
measured in Coulombs (C). One electron has a charge of 1.6x10-19 C. 1 Coulomb is defined as the amount of charge that passes in 1 second when the current is 1 Ampere.
what is current?
the rate of flow of charge, and is measured in Amperes (A). A current of 1A means that 1 coulomb of charge flows past that point every second (hence the term “rate”). Current can only flow if there is a potential difference. It is measured with ammeters which are placed in series within a circuit
what is potential difference?
measured in volts (V), and is the work done per unit charge. It is measured by voltmeters that are placed in parallel and have infinite resistance, so they measure current between 2 points in a circuit.
what is resistance?
measured in Ohms (Ω). It slows down the current passing through the circuit.
what is power?
measured in watts (W) and is defined as the rate of transfer of energy
how are cell connected in series and parallel different?
series- total voltage is the sum of individual voltages
parallel- total voltage is equal to one cell
what’s the point in having cells connected in parallel if the voltages don’t sum?
There are two main reasons - firstly, the batteries each last twice as long as they would if they were connected in series, and secondly, if one of the batteries were to die/break, the circuit would still be operational.
what is the equation that links potential difference (V), current (I) and resistance (R)?
V=IR
how do resistors differ in series and parallel?
series- their resistances are added together to get the total resistance.
parallel- total resistance is less than individual resistor
why are cells different in series and parallel?
-In series, each ‘push’ (voltage) that the batteries provide is different so they are added together.
-In parallel, an electron can only ever go through one cell in each ‘lap’ of the circuit, so it only gets one push
How does current differ in series and parallel circuits?
series- current is the same throughout the circuit
parallel- the sum of currents flowing into a junction must equal the sum of currents leaving the junction (Kirchoff’s First Law)
how does voltage differ in a series and parallel circuit?
series- total voltage supplied by the cell is divided between the components
parallel- the voltage supplied by the cell is the same as the voltage across each component in the circuit.
what does it mean by short circuit?
the charge bypasses the component by taking the path of least resistance
what is a diode?
a device allowing the flow of current in one direction
what happens if the arrow of the diode is pointing in opposite direction to the current?
the diode is in “reverse bias” and no charge can pass through
how does current flow?
from positive to negative
what is a transformer?
a device that changes voltage and current, whilst keeping power the same
what is the equation where n1 is the number of turns on the primary coil and n2 is the number of turns on the secondary coil. Naturally, v1 and v2 are each coil’s respective voltage.
n1/n2=V1/V2
what happens If the secondary coil has more turns than the primary?
the voltage is stepped up (ie: increased) and the current is decreased
what happens if the primary coil has more turns?
then the voltage is decreased (this is helpful when electricity has reached houses to step it down to a more manageable voltage) and the current is increased.
transformers only work with what kind of current?
Alternating Current (AC). They do NOT work with Direct Current (DC).
voltage is only created when?
he magnet is moving. Moving the magnet in one direction would generate a positive voltage, whereas moving it in the other direction would generate a negative voltage.
what happens when you keep moving the magnet backwards and forwards through the coil?
you create a potential difference that keeps on changing direction - an Alternating Current (AC).
how do generators work?
by spinning the magnet in the coil instead of moving it in and out
