Electricity Flashcards
(34 cards)
charge equation
current x time
Q = It
potential difference
current x resistance
V = IR
power with v and i
potential difference x current
power with i and r
current x resistance
energy transferred
power x time
energy transferred with q and v
charge flow x potential difference
Series Circuits
Components that are connected one after another on the same loop of the circuit are connected in series
The sum of all the potential differences across the components in a series circuit is equal to the total potential difference across the power supply.
Two lamps connected in series
If one lamp breaks, the other lamp will not light.
Parallel Circuits
- Components that are connected on separate loops are connected in parallel.
- The current is shared between each component connected in parallel.
- The total amount of current flowing into the junction, or split, is equal to the total current flowing out.
- The current is described as being conserved.
- For a parallel circuit the current from the electrical supply is greater than the current in each branch. The sum of all the current in every branch is equal to the current from the electrical supply.
Two lamps connected in parallel
If one lamp breaks, the other lamp will still light.
AC
If the current constantly changes direction it is called alternating current, or AC. Mains electricity is an AC supply. The UK mains supply is about 230 V. It has a frequency of 50 Hz, which means that it changes direction and back again 50 times a second.
DC
If the current flows in only one direction it is called direct current, or DC. Batteries and solar cells supply DC electricity. A typical battery may supply 1.5 V.
how to get electrocuted
touching frayed electrical cables long or overheating cables damaged or incorrectly wired plugs allowing water or wet objects to enter plug sockets or touch frayed cables pushing metal objects into plug sockets
BRown
Live Is held at a voltage of 230 V and provides the current - Goes Right
BLue
Neutral Completes the circuit - Goes Left
Green and yellow stripes
Earth A safety wire to stop the appliance becoming live
Fuse
The fuse breaks the circuit if a fault in an appliance causes too much current to flow. This protects the wiring and the appliance if something goes wrong. The fuse contains a piece of wire that melts easily. If the current going through the fuse is too great, the wire heats up until it melts and breaks the circuit.
Electric current is
the rate of flow of electric charge.
How does electricity pass through metallic conductors
Electricity passes through metallic conductors as a flow of negatively charged electrons. The electrons are free to move from one atom to another. We call them a sea of delocalised electrons.
Voltmeters
Measuring potential difference (voltage)
Potential difference is measured in volts, V
the potential difference across a component in a circuit is measured using a voltmeter
the voltmeter must be connected in parallel with the component
Ammeter
Measuring current
current is measured in amperes (amperes is often abbreviated to amps or A)
the current flowing through a component in a circuit is measured using an ammeter
the ammeter must be connected in series with the component
Resistance in a wire
The resistance in a wire increases as:
the length of the wire increases
the thickness of the wire decreases
Resistance of a long wire
The resistance of a long wire is greater than the resistance of a short wire because electrons collide with more ions as they pass through. The relationship between resistance and wire length is proportional.
Why is there resistance in a wire ?
An electric current flows when electrons move through a conductor, such as a metal wire. The moving electrons can collide with the ions in the metal. This makes it more difficult for the current to flow, and causes resistance.
