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National 5 Physics 2015-2016

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Original post by alex5023
Also what about the question about the washing machine where it gave you a circuit with a transistor and you had to explain how the heating element would switch off?


I wrote that the thermistor detects when the temperature of the water reaches 40 degrees. Then the resistance of the thermistor increased which means the current was going to reduce. If the current reduced the voltage would reduce as well which would eventually be less than 2.0v and then the MOSFET transistor would not work anymore so current wouldn't flow

I didn't know what to say about the relay switch because I couldn't remember anything about that...

Can someone mark this answer please? :smile:
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Hmm I wrote that the resistance remains constant for that one.
Original post by sameehaiqbal
I wrote that the thermistor detects when the temperature of the water reaches 40 degrees. Then the resistance of the thermistor increased which means the current was going to reduce. If the current reduced the voltage would reduce as well which would eventually be less than 2.0v and then the MOSFET transistor would not work anymore so current wouldn't flow

I didn't know what to say about the relay switch because I couldn't remember anything about that...

Can someone mark this answer please? :smile:


The resistance of the thermistor decreases so voltage decreases and then when this falls below 2.0v the MOSFET turns off. So the relay switches of the heater
Original post by ___Sophie___
I got 5 ohms. But the question said use all the values in the table for some odd reason so i calculated the resistance four times and I got 5 ohms for all of them

That was what I did
What about the question that you had to put the forces on to the diagram?
I got air resistance
Weight (of the person)
Force of friction (due to the rope thing)
What did you all put?
Original post by Marina1264
That was what I did


Yeah I think there were a couple of methods you could have used :smile:
Original post by ___Sophie___
What about the question that you had to put the forces on to the diagram?
I got air resistance
Weight (of the person)
Force of friction (due to the rope thing)
What did you all put?

I just did air resistance upwards and weight downwards
Original post by 12345kiran
I just did air resistance upwards and weight downwards


Not sure what the correct answer was. Do you remember how many marks it was worth?
Original post by sameehaiqbal
I wrote that the thermistor detects when the temperature of the water reaches 40 degrees. Then the resistance of the thermistor increased which means the current was going to reduce. If the current reduced the voltage would reduce as well which would eventually be less than 2.0v and then the MOSFET transistor would not work anymore so current wouldn't flow

I didn't know what to say about the relay switch because I couldn't remember anything about that...

Can someone mark this answer please? :smile:


Anyone else??? :smile:
Original post by ___Sophie___
Not sure what the correct answer was. Do you remember how many marks it was worth?


3. Two for the forces and one for the directions
Original post by 12345kiran
3. Two for the forces and one for the directions


Ok thanks
Original post by ___Sophie___
What about the question that you had to put the forces on to the diagram?
I got air resistance
Weight (of the person)
Force of friction (due to the rope thing)
What did you all put?


Original post by 12345kiran
I just did air resistance upwards and weight downwards


Done Weight down, Air resisitance up.
What did you guys all put for the metal poll?
Lmao hahah idk what I was thinking but for the top arrow I put friction, I think the stress got to me lol. I think I only lost a mark tho so its alright
Original post by 12345kiran
What did you guys all put for the metal poll?


What question was that? I don't remember any metal poll....
Original post by 12345kiran
What did you guys all put for the metal poll?


Are you talking about the thing on the building?
I said that metals are positively charged so when there is a lightning storm, the negatively charged electrons from the lightning will be attracted to the positively charged metal pole because opposite charges attract therefore the lightning will not touch the building it will only touch the pole.
Original post by sameehaiqbal
I wrote that the thermistor detects when the temperature of the water reaches 40 degrees. Then the resistance of the thermistor increased which means the current was going to reduce. If the current reduced the voltage would reduce as well which would eventually be less than 2.0v and then the MOSFET transistor would not work anymore so current wouldn't flow

I didn't know what to say about the relay switch because I couldn't remember anything about that...

Can someone mark this answer please? :smile:


That's what I wrote too, not exactly but pretty close. You'll definitely get 2 marks at least
Wish someone could get section 2 - it's gonna be so hard waiting under 2 months just to see my grade :frown:
Original post by ___Sophie___
Are you talking about the thing on the building?
I said that metals are positively charged so when there is a lightning storm, the negatively charged electrons from the lightning will be attracted to the positively charged metal pole because opposite charges attract therefore the lightning will not touch the building it will only touch the pole.


That's a really good answer, wish i thought of that in the exam. I wrote something really stupid haha
Original post by sameehaiqbal
Wish someone could get section 2 - it's gonna be so hard waiting under 2 months just to see my grade :frown:


I knoww :/ I'm really scared

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