Download Summary notes Electricity and light

Kelso High School
S2 Electricity and Light
Summary Notes
Name …………………………………………………………..
Class ………………………..
Electricity
Circuit symbols are used to draw electric circuit diagrams.
name of
component
name of
component
symbol
Cell / battery
switch
wire
voltmeter
lamp
fuse
resistor
ammeter
variable resistor
motor
You should be able to draw simple circuit diagrams following
the rules
symbol
V
A
M
Always use
a pencil
and ruler
Make wires
straight with
right angles
Make sure
wires touch
components
Never draw
components
at the corners
Electric current flows through the wires in a circuit when there are no
gaps in it.
An electric current is a flow of small particles called electrons (similar
to water flowing through a pipe). They are negatively charged so go
from the negative terminal to the positive terminal
Electrons carry energy around a circuit.
A series circuit has only one
path for the current to take.
A parallel circuit has more than
one path for the current to take.
1
4
An ammeter measures the size of a current in Amps (A).
An ammeter is connected in series in a
circuit.
The current in a series circuit is the
same at all points
A2
3
I1 = I2 = I3 = I4
AT
The current in the branches of a parallel circuit add up to the total current
IT = I1 + I2 + I3
A1
A2
A3
A battery gives energy to the electron and ‘pushes’ it around a circuit.
A voltmeter measures the size of
the ‘push’ in volts (V).
A voltmeter is placed in parallel
across a component to measure voltage.
V
supply
V
1
V
2
The voltage in a series circuit adds
up to the voltage of the supply
supply
1
Vs = V1 + V2
2
The voltage in a parallel circuit is
the same across each component.
3
Vs = V1 = V2 = V3
You should be able to work out the current
at different parts of a circuit.
Put your finger at the negative side of the
battery and trace the route through the
bulb and motor.
There is only one path so all the current
goes through the bulb and the motor. The
route then splits into two , If the resistors
are the same strength half the current will
go each way. The current joins together
again so the current at position 3 is the
same as through the bulb.
3
1
M
2
Current
Current
Current
Current
Current
through bulb = 6A
through motor = 6A
through resistor 1 = 3A
through resistor 2 = 3A
at position 3 = 6A
Light
The law of reflection
The angle of incidence equals the angle of reflection
Normal
Angle of incidence
Angle of reflection
Mirror
You should know some uses for reflection
Car head light
Periscope
Endoscopes use
total internal reflection
Refraction is when waves change
speed due to travelling in a different
medium.
You should be able to draw these ray diagrams
Concave lens
Convex lens
You should know some uses of refraction.
glasses
camera
microscope
telescope
binoculars
You should be able to label these parts of the eye.
Retina
Iris
Optic nerve
Pupil
Cornea
Lens
Cillary muscles
Blind spot
The pupil lets light into your eye. When it is dark your pupil is large
to let in more light. When it is bright your pupil is small so that too
much light doesn’t get in.
Pupils size in the dark
Pupils size in the light
The lens focuses light on the back of your eye. A thin lens bends
light less than a fat lens.
The shape of your lens changes to allow you to see near and far objects sharply
The retina picks up the light that lands on it and sends a message to
your brain.
The blind spot is the one place on the back of your eye where there is
no retina so the picture is not seen
Your eyes and brain can be tricked. Optical illusions can fool you, so
it’s a good idea to always measure things and not just rely on looking
at them
Different colours of light refract by different amounts.
Write how you could
remember the order
here.
White light
Refracted least
Red
Orange
Yellow
Green
Blue
Indigo
Violet. Refracted most
Glass prism
Colour addition of light.
cyan
Blue
magenta
white
red
green
yellow
Adding blue and red makes magenta (purple)
Adding blue and green makes cyan (light blue)
Adding red and green makes yellow
Adding red, blue and green makes white.
Test Yourself Questions Electricity
1. For each of the photographs draw a circuit diagram.
(a)
(b)
switch
motor
bulb
Bulb
switch
fuse
Bulb
2. Which of the above circuits shows a series circuit?
3. Do electrons have a negative or positive charge?
4. (a) Draw a series circuit using 2 batteries, a bulb and a motor.
(b) Put an arrow on your circuit to show the direction the current
flows in.
(c) Add a voltmeter across the motor.
(d) If the current through the bulb is 2A what is the current through
the motor?
(e) If the voltage across the motor is 3V and across the bulb is 2V.
What is the supply voltage?
5. Do the electricity quiz you will find in the learning resources.
Test Yourself Questions
Light
1. State the law of reflection.
2. Name at least 2 things that use reflection.
3. What always changes when light goes from air into glass?
4. Draw a ray diagram for a concave lens.
5. Name at least 3 things that use refraction.
6. What does the pupil in your eye do?
7. Which part of your eye detects the light?
8. Will a thin or thick lens bend light the most?
9. List the colours of a rain bow starting with the one that refracts the most.
10.What 3 colours are needed to make white light?
11. Which 2 colours make yellow light?
Answers
Electricity
1. (a)
(b)
M
2. (b) 3. negative
3.
4. (d) 2 A
(e) 5 V
M
V
Answers
Light
1. The incident angle equals the refracted angle
2. Mirrors, periscopes, torches, endoscopes, car head lights and many
more.
3. Speed
4.
5. glasses, camera, telescope, microscope, binoculars and many more.
6. Lets light into your eye. 7. Retina 8. Thick
9. Violet, indigo, blue, green, yellow, orange, red. 10. Red, blue, green
11. Red and green.