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physics
paper 2
topic 10 - electricity and circuits
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Cards (17)
current
flow of electric charges
measured in
amps (A)
has the same value at every point in a single closed loop
current equation
current =
charge
/ time
symbol equation for charge
Q
=
I
x
T
electrical insulators
materials that don't allow
electric current
to pass through them
e.g.
plastic
and
glass
electrical conductors
has lots of free charges (
electrons
in metals) that are able to move
current
going through metal is the movement of these electrons through the metal
potential difference
measured in
volts
energy
transferred per unit charge in a
circuit
.
It tells us how much energy each
coulomb
of charge gains or loses as it moves between two points.
coulomb
the unit of
electric charge
. It tells us how much electric charge is flowing in a circuit.
quantity
- like a litre of water, coulomb measures electrical charge
p.d. / voltage equation
v =
energy transferred
/
charge
potential difference
of
one volt
=
1 joule
of energy being used by a
coulomb
of charge when it flows between
2 points
on a circuit
ammeter
measures flow of current that passes through it
have to be connected in series (in the same loop of the circuit) of the component you're measuring
voltmeters
measures
pd
between 2 points in a circuit
must always be connected in
parallel
(on seperat
branch
of circuit) to points being measured
energy, voltage and charge equation
E = QV
Why do resistors become warm
collisions between
electrons
and
lattice
Lattice moves more causing more heat
3 wire plug
Brown-
live wire
. Carries current into appliance
blue-
neutral wire
. Completes circuit by carrying current away, close to
0V
Green/yellow
- safety feature, prevents appliance from becoming live, only connected to metal casing, only carries current if there is a fault
Fuse
thin wire that melts and breaks circuit if
current
= too high
protects
appliance
, prevents fires
fuse melts and stops flow of electricity
Purpose of earth wire
prevents metal case from becoming
live
By carrying current to the
ground
why would a kettle need an earth wire
case = metal, could become live if
live wire
touches it
earth wire provides
low resistance
path for current to flow to ground
causes
fuse
to blow and break circuit