Electricity and Circuits Flashcards
what is the difference between series and parallel circuits?
series- components connected in line, same current everywhere, p.d. shared
parallel- separately connected, same p.d., current shared
what is potential difference?
energy transferred over unit charge
what is a volt?
p.d. is sometimes called voltage, same thing
what is the equation for energy transferred?
energy transferred= charge moved X potential difference
E= Q X V
what is current?
- flow of electrical charge e.g. electrons
- only flow if there is is p.d.
- circuit must be complete
what is the equation for charge?
charge= current X time Q= I X T current in A Charge in C Time in s
what happens to current at a junction in a circuit?
current is conserved at a junction in a circuit
what is resistance and what is it measured in?
anything that slows the flow down
measured in ohm
what is the equation for potential difference?
potential difference= current X resistance
V= I X R
what happens when you add a resistor in a series circuit?
- increases total resistance
- because they have to share total p.d.
- and the current is the same everywhere
what happens when you add resistor in a parallel circuit?
- reduces total resistance
- increase in current meaning decrease in total resistance
what is the current like in a series circuit?
-current same everywhere
I= V / R
what is the potential different like in a series circuit?
-total p.d. of supply is equally shared
what is the resistance like in a series circuit?
-increases as you add resistors
what happens if one component isn’t working in a series circuit?
nothing will work
what is the method of practical used to investigate the relationship between V, I, and R for resistor and filament lamps?
- set up circuit with ammeter, cell, resister, and voltmeter under component
- change resistance and measure current
- take several pair of readings
- plot current against p.d. on I-V graph
- you can then see relationship
what happens when you add a diode as the component in the circuit?
if you swap its direction current cannot flow through it
what happens when you add a thermistor as the component in the circuit?
as you heat it current increases and resistance decreases
what happens when yours LDR’s (filament lamps) as the component in the circuit?
light will get brighter, current increases and resistance decreases
what happens when there is an electric current in a resistor?
there is an energy transfer which heats the resistor
LEARN GRAPHS ON PAGE 187
LEARN GRAPHS ON PAGE 187
what equation can we use to work out energy transferred to and electrical component?
E= I X V X t
what are the advantages of the heating effect on an electrical circuit?
- toasters, containing a coil of wire
- similar to filament bulbs and electric heaters
what are the disadvantages of the heating effect on an electrical circuit?
- reduces efficiency
- too high, could melt
what is power? what is it measured in?
- energy transferred per second
- measured in watts
what is the equation for power?
P= E/t power(W)= energy transferred(J) / Time(s)
how is the power transfer in a circuit related to the potential different and current in it?
- p.d. tells you energy each unit of change transfers
- currents tells you how much charge passes per unit time
- so both effect energy transferred to appliance
what is the equation for electrical power?
-P= I X V
e.p. (W)= current(A) X p.d.(V)
OR
-P= I2 X R
e.p.(W)= current squared (A) X resistance (ohm)
what is direct current?
-charges move in same direction
what is alternating current?
-charges constantly changing direction
what supplies direct current?
cells and batteries
what is the UK domestic electric supply (d.c. or a.c.) and whats the voltage and frequency?
- alternating current
- frequency= 50Hz
- voltage= 230V
what is the function of a live wire in a plug?
- brown
- carries voltage
- around 230V
what is the function of a neutral wire in a plug?
- blue
- completes circuit
- generally electricity goes in live wire and out neutral wire
what is the function of the earth wire in a plug?
- green/yellow
- safety and protecting wiring
- stop appliance becoming live
what is the function of a fuse in a plug?
-prevent electrical overloads
why should switches and fuses be connected in a live wire of a domestic circuit?
-so the current can be broken
what is the function of a circuit breaker and why is it better than a fuse?
- will trip instead of melting fuse
- turn off quicker
- can be reset instead of replaced like a fuse
what is the potential difference between live and earth wires?
230V
what is the potential difference between the live and neutral wire?
230V
what is the potential difference between the neutral and earth wire?
0V
what are the potential dangers of the live wire and earth?
- electrical shock
- fire
- current flowing through body
