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Get better at Circuit questions? (EMF, Internal resistance, potential dividers, etc)

It's all confusing and nothing makes sense.

Physics is the only subject that's currently pulling me down and I don't know how I can improve at all.

Some help would be nice.
Just do a crap tonne of questions. The only way really.
What about questions with like internal resistance and etc.

Thanks for that btw.
Could you explain the answer in a mark scheme for me?
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Q:

The temperature of the thermistor is increased so that its resistance decreases. State and explain what happens to the pd across the 1200 Ω resistor.

A:
(voltage of supply constant) (circuit resistance decreases) (supply) current increases or potential divider argument (1)

hence pd across 540 Ω resistor increases (1)

hence pd across 1200 Ω decreases (1) or

resistance in parallel combination decreases (1)

pd across parallel resistors decreases (1)

pd across 1200 Ω decreases (1)

why does the current increase? I swear current always stays the same.

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