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Physics risk assessment

Hiya Guys!

Any idea what risks and hazards there could be for an experiment to do with LDRs. I've come up with with the lamp bulb being hot but I need two more. Any help is much appreciated!!!
Reply 1
Avatar for panda14
panda14
3
Electricity - usual stuff, shock, fire and burns if short circuited, Use an RCD protected circuit, minimum live time and output voltage.
Other people in the lab - based on what work they're doing.
Lab furniture - trips and falls, hitting head on cupboard over side benches etc.



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Hi my students often short circuit power supplies and have had minor burns touching hot wires if trip didn't work. One student plugged a 12v Ray box into the mains outlet and was thrown backwards. The whole lab power tripped...
Reply 3
Avatar for amjam441
amjam441
OP
12
Original post by Slenderlorris
Hi my students often short circuit power supplies and have had minor burns touching hot wires if trip didn't work. One student plugged a 12v Ray box into the mains outlet and was thrown backwards. The whole lab power tripped...


LOL :tongue:
Original post by amjam441
Hiya Guys!

Any idea what risks and hazards there could be for an experiment to do with LDRs. I've come up with with the lamp bulb being hot but I need two more. Any help is much appreciated!!!


If I do that right, the resistor of LDRs depend on the light. The more light rays touch the LDR, the lesser the resistor. That is to say the current (and so electricity) increases. In my consideration that may lead to a short circuit in the LDR, when the current is higher than the operating current and the resistor too less.
Reply 5
Avatar for amjam441
amjam441
OP
12
Hi me again.

Just needed help explaining why changing the voltage would affect the resistance of the LDR i.e it wouldn't be a fair test (if you could GCSE friendly explanations that'd be great) :smile:
Reply 6
Avatar for panda14
panda14
3
Original post by Slenderlorris
Hi my students often short circuit power supplies and have had minor burns touching hot wires if trip didn't work. One student plugged a 12v Ray box into the mains outlet and was thrown backwards. The whole lab power tripped...


I hope they were Ok! I have to say all our power supply circuit breakers go off so quickly it's painfully hard to do some experiments, but better safe than sorry! Are you changing the PD as a means of changing current? If I'm honest it sounds like a potential divider situation, which I don't think is normally GCSE material. Or doing AS means I can't cop with simple stuff anymore, which is more likely!

Sorry. :frown:
(edited 8 years ago)
Original post by amjam441
Hi me again.

Just needed help explaining why changing the voltage would affect the resistance of the LDR i.e it wouldn't be a fair test (if you could GCSE friendly explanations that'd be great) :smile:


After R = U/I, changing the voltage means that the resistor would decrease or increase (if the current is not changed). Increase voltage leads to a reduced resistor, but vice versa it raises.

As I wrote before, the resistor in an LDR depends on the light. And if many light rays touches the LDR, the resistor is very less. To prevent such a reduced resistor, the voltage can be decreased, I think so.

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