Transcript practical tech`s

Practical Technique 1 Speed
Instantaneous speed – the speed at one point in the journey.
Measure the length of the mask, d.
Measure the time for mask to go through the light gate, t.
Calculate the average time.
Calculate the speed, v = d ÷ t. Remember if distance is in
metres speed will be in m/s, if distance is in centimetres speed
is in cm/s
Practical Technique 2 Focal Length
A distant object will appear as an upside down image on the
card. Measure the distance between the card an the lens
when the image is in focus. This is the focal length of the
lens.
The power of the lens is 1÷ focal length and is measured in
dioptres(D)
Practical Technique 3 Refraction
Refracted
ray
normal
Incident
ray
Normal – a line at right angles to the boundary
Incident angle – between the normal and the incident ray.
Refracted angle – between the normal and the refracted ray.
Practical Technique 4 Circuit Faults
Space for testing
Continuity tester –
only tests for open
circuits

Using an ohmmeter to test for open and short circuits. Power
source must be disconnected,
Open circuit will give a very high resistance.
Short circuit will give a lower than expected resistance.
Practical Technique 5 V and I
Ammeter needs one extra
wire and is put into the circuit
Voltmeter needs two extra
wires and is put across the
component.
Practical Technique 6 Peak Voltage
The peak voltage is the amplitude of the wave.
Peak voltage = no. of boxes from middle to peak x volts per division
Practical Technique 7 Voltage Divider
R2
Vt
R1
Rt = R1 + R2
V1 =
R1 Vt
Rt
1. Connect the power supply to
each end of the variable
resistor.
2. Connect the voltmeter to one
end of the resistor and the
middle connection.
3. Turn the variable resistor
until you get the correct
reading on the voltmeter.
Practical Technique 8 Circuit
switch
resistor
wire
V
A
voltmeter
ammeter