Magnetism
Describe the term magnetic field?
A magnetic field is the area around a magnet where the magnet experiences a force
Define AC voltage
Electrons of the current flow oscillate forward and then backward in the circuit
What is ohms law?
V I R
What is the purpose of touching the leads together on a multimeter?
To confirm that the test leads are connected and continuous
What happens to an extension lead if it is not fully unwound?
The lead could from induction when carrying current
Describe how magnets with like poles behave?
Like magnetic poles repel
What is the calculation for impedance in an AC circuit?
I = V/Z
Explain Flemings left hand rule
DOUBLE POINTS
Show the orientation of the hand and explain what the right hand is used for electrically
Movement - Thumb
Field - First finger
Current - Second finger
Motors
ITS A ROBBERY!
What is the first step in the isolation procedure?
Communicate with the customer
Where in a circuit should the RCD be placed?
At the power supply
Describe how magnets with opposite poles behave?
Opposite magnetic poles attract
ITS A ROBBERY!
What is the frequency in NZ?
50 or 60hz
List three commonly used electromagnets
Any three of the below
Solenoids Relays
Contactors MCBs
Bells Speakers
What must your lock out tag have on it?
Name
Contact phone number
What safety feature does a class 1 appliance have?
An earth connected to exposed metal work to the earth pin of the plug
How does an electromagnet work?
A magnet that gets its magnetism from a coil of wire with an electrical current flowing through it
What is the formula for peak RMS voltage?
x .707
Explain the difference between switching off & Isolation?
Switching off stops an electrical appliance or circuit from going or working.
Isolation is disconnection from an electrical energy source & prevents the circuit from being unintentionally re-energised
Explain prove test prove
Prove the tester is working on a known live source
Test for isolation
Prove the tester is working on a known live source again
What is a safety feature of a class 2 appliance?
Instead of earthing the exposed metalwork, there is a double layer of insulation between any live conductors & the outside of the appliance
Explain Flemings right hand rule
DOUBLE POINTS
Show the orientation of the hand and explain what the right hand is used for electrically
Movement - Thumb
Field - First finger
Current - Second finger
Generators
Define impedance
DOUBLE POINTS TO NAME THEM
Total opposition to current flow
Resistance
Capacitance
Inductance
ITS A ROBBERY!
Explain the connection of an Edison screw light fitting
The neutral conductor is connected to the outer sheath, Phase is connected to the centre terminal
What is the definition of isolation?
Isolation is disconnection from an electrical energy source for safety reasons
What voltage rating do insulated tools need?
1000v