Electrical Safety

Question 1

What is the advantage of AC?

Answer 1

• Easier to generate
• Cheaper
• Easier to use (switch off, transform, convert to DC)

Question 2

How does a single phase alternator work?

Answer 2

1) Coil of wire between magnets
2) Coil turned by some form of energy (steam/burning fossil fuels
3) Rotates coil between 2 magnets
4) Generates magnetic field which can have affect on current and vice versa
5) As wire moves between North & South poles of magnets becomes +ve & -ve = AC

Question 3

In what type of current can you get an ‘arc’ of electricity?

Answer 3

DC

Question 4

Why can you get an electrical arc in DC current?

Answer 4

• When in a circuit power supply provides voltage (push of current)
• When opening switch initially switch opened by tiny amount
• All voltage pushes at switch
• If only small jump and voltage above that of surrounding air electron pushed out of O2 causing spark
• Spark releases heat which ionises surrounding air causing further current = arc

Question 5

How does a transformer work?

Answer 5

• Only works for AC
• 2 coils on either side of a magnetic core- no connection between coils
• Current flows through one coil which generates current in other coil due to magnetic field
• Can use to convert one voltage to another by the under of coils in the wire

Question 6

What are the disadvantages of AC?

Answer 6

• Electromagnetic induction: Power/energy loss, interference
• Electrostatic induction: interference

Question 7

What does the effect of an electric shock depend on?

Answer 7

• Magnitude of current
• Frequency
• Period over which applied
• Relationship to cardiac cycle