P2 Topic 1: Static and Current Electricity
Friday, 13 March 2015
Additional Science Revision
Model Answers
1
In the nucleus
Neutral
1
In the nucleus
-1
negligible
Orbiting the nucleus
+1
Electrons are transferred by friction from the cloth to
the rod.
Negative
Positive
Metals are good conductors so electrons move easily through and are
spread out.
P2 Topic 1: Static and Current Electricity
Friday, 13 March 2015
Additional Science Revision
Model Answers
electrons
positively
electrons
electrons
the object now has more protons than electrons so is positively charged
negatively
the object now has more electrons than protons so is negatively charged
attract
repel
repel
P2 Topic 1: Static and Current Electricity
Friday, 13 March 2015
Additional Science Revision
Model Answers
E.G shock from a door handle:
Charge builds up on the person as they walk
across the floor due to friction between the
shoes and carpet transferring electrons. When
the person touches the metal door handle, the
charge flows through the metal to the earth. The
person feels a shock from this flow of charge.
The balloon is negatively charged. The wall has
both positive and negative charges in it but
overall has no charge. When the balloon is held
near the wall the electrons in the wall are repelled
and move away. The positive charge (induced
charge) left behind attracts the negatively
charged balloon so it sticks to the wall.
Static charge builds up in the clouds by friction
between ice particles in the air transferring
electrons. The charge build up in the cloud can
induce an opposite charge in the ground. If the
difference in charge is big enough a huge spark
will form (the lightning bolt)
The comb has a charge (for example negative).
When it is held near some neutral paper the paper
electrons in the paper are repelled, leaving a
positive charge near the comb. This side of the
paper is attracted to the comb.
P2 Topic 1: Static and Current Electricity
Friday, 13 March 2015
Additional Science Revision
Model Answers
Friction between the air and the aircraft. As the aircraft
passes through the air, friction transfers electrons and the
plane becomes charged.
the build up of charge can cause a spark which
could ignite the fuel
attaching a bonding line (a metal wire) which connects the aircraft to the earth.
This discharges the aircraft before it is refuelled so there are no sparks near
the fuel line.
P2 Topic 1: Static and Current Electricity
Friday, 13 March 2015
Additional Science Revision
Model Answers
The paint is charged in the paint sprayer so the droplets
will have the same charge and therefore repel each other.
This means the paint droplets spread out so form a fine,
even spray. The paint is charged in the opposite way to the
object so the paint is attracted to the object and is not
wasted.
The pesticide is charged in a crop sprayer so the pesticide
spreads out evenly. Less pesticide can then be used to
guarantee sufficient coverage across the whole field.
P2 Topic 1: Static and Current Electricity
Friday, 13 March 2015
Additional Science Revision
Model Answers
charge
current
cell
bulb
P2 Topic 1: Static and Current Electricity
Additional Science Revision
Model Answers
The atoms are arranged in a regular way
Move between one ion and the next
sea of delocalised electrons
they repel and so electrons are pushed round the circuit
Friday, 13 March 2015
P2 Topic 1: Static and Current Electricity
Friday, 13 March 2015
Additional Science Revision
Model Answers
5A
Q=Ixt
30s
Q = 5 x 30
150 C
Q=Ixt
30s
150 C
I = Q/t
I = 150/30
5A
A cell is a single unit while a battery is made of
several cells connected together in series
Current is generated by a wire moving in a magnetic
field. If the wire is moved in the opposite direction, the
induced current also moves in the opposite direction.
In a generator, the coil moves up during one half turn,
and then down during the next half turn.
This means that as a coil is rotated in a magnetic field,
the induced current reverses direction every half turn.
This is called alternating current (AC).
Batteries produce electricity by a
chemical reaction. Batteries have 3
parts – anode (-ve), cathode (+ve) and
electrolyte. The chemical reactions
cause electrons to build up at the anode
so there is a electrical difference
between the anode and the cathode. The
electrons repel each other and flow
through the wires to the place with a
lower number of electrons. They can’t
travel straight from anode to cathode
because of the electrolyte.
P2 Topic 1: Static and Current Electricity
Friday, 13 March 2015
Additional Science Revision
Model Answers
AC – current
reverses
between
positive and
negative
direction
DC – current in
positive
direction only
AC – current
reverses
between
positive and
negative
direction
DC – current in
positive
direction only
DC – current in
positive
direction only