Occupational Health And Safety Ngc2 (Element 5)

Front 1

Relationship between current, resistance & voltage in a simple circuit?

Back 1

Ohm's law:
Voltage = Current x Resistance or V = I x R

Front 2

Main effects of electric shock on body?

Back 2

Muscle tremor and contractions (often violent). Can also result in heart beating spasmodically (ventricular fibrillation) or cardiac arrest. Also can result in burns.

Front 3

Shock for 1 sec with resistance of 10,000 ohms
What is current & effects with 240 Volts?

Back 3

I = V/R = 240/10,000 = 24 mA
Strong muscle contraction.
Possible breathing difficulties.

Front 4

Shock for 1 sec with resistance of 10,000 ohms
What is current & effects with 110 Volts?

Back 4

I =V/R = 110/10,000 = 11 mA
Pain and some muscle contraction.

Front 5

Shock for 1 sec with resistance of 10,000 ohms
What is current & effects with 50 Volts?

Back 5

I = V/R = 50/10,000 = 5 mA
Perhaps mild tingling.

Front 6

First step of treating victim of electric shock?

Back 6

Break any continuing contact between victim & current.

Front 7

Arcing?

Back 7

Electrical bridging through air from one conductor to another.
Victim may be burnt.
Electric shock.
May be burnt from ultraviolet radiation & radiated heat even when arc does not touch the person.
Can be source of ignition for fire.

Front 8

Earthing?

Back 8

Provides a safe path for any fault current to be dispersed to earth through a low resistence conductor.

Front 9

Protection cord grip in plug?

Back 9

Restricts movement at point of entry of the flexible cable into the plug, preventing abrasion of the cable. It also prevents the conductors been pulled loose from their terminals.

Front 10

Difference between a fuse and circuit breaker?

Back 10

Fuse forms a weak link in a circuit by overheating and melting by design if the current exceeds the safe limit. A circuit breaker is an electro mechanical device in the form of a switch which automatically opens if the circuit is overloaded.

Front 11

Difference between switching off and isolation?

Back 11

Switching off refers to depriving the equipment of electric power but still leaving it connected. Isolation refers to physically separating it from any source of electric power, with the additional step of ensuring it cannot inadvertently re-energised.

Front 12

What protection by reduced low voltage transformer used to provide power to hand tools?

Back 12

Resduced low voltage circuits reduce the effect of any shock received from making contact with poart of the circuit because of the relationship between voltage & current. If resistance stays the same then less votage means less current.

Front 13

What safety device for mains tools used outdoors?

Back 13

If they cannot be powered by battery, Then a residual current device should be used.

Front 14

What user checks before operating a piece of electrical equipment.

Back 14

Damage to cable sheaths, joints or plugs.
Evidence it has been subjected to conditions it was not suitable e.g wet or contaminated.
Damage to external casing or loose parts or screws.