10.3a Ex1 MJ16 P11 Q37 Motor Potential Divider Circuit | AS DC Circuits | Cambridge A Level Physics

Example 1 - 9702/11/M/J/16: A voltmeter is used to monitor the operation of an electric motor. The motor speed is controlled
by a variable resistor. A fixed resistor is used to limit the speed. The current in the motor is gradually changed. In which circuit is the voltmeter reading proportional to the current in the motor?
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9702_s16_qp11

[@nowerabony8155]

it can be done more easily :3 for v to be proportional to R, there must be a constant, but in a and c, the voltmeter is connected to a variable resistor whose resistance might vary; and in d, there is no constant, but we need a constant for something to be proportional. Only in B, the voltmeter is connected to a fixed resistor, which is constant, thus v= IR where if R is the constant, we can say that v is proportional to R

[@hason.z9729]

But V has to be proportional to I, not R

[@BOBO_4869]

@@hason.z9729 I think they meant "V to be proportional to I", since if that applies, finding the constant R is the aim - which apparently it is, according to the proceeding explanations (If there is a variable resistor then R won't be constant; as such, V can't be proportional to I)

[@ARGAMING-pb9yv]

Thanks!

[@BOBO_4869]

TYSM!!!!!!!!!!

[@xinyu9036]

Teacher for A, why do we know that Vc is decreasing when Rv is decreasing and current is increasing? 7:34

[@chickunt3nders]

the what now

[@saadrr1697]

facts

[@YourBoyDany]

I hate this chapter

[@lowkeycam9151]

@@YourBoyDany i agree why tf does it even exist

[@bilaltaj1725]

@@lowkeycam9151 lol, do you think that this the hardest chapter in AS physcis?

[@lowkeycam9151]

@@bilaltaj1725 personally for me, im done with the entire syllabus and still find this the hardest one