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Circuits, Oxford Physics sample

Hi
I haven't had the same syllabus as UK students so please bare with me.
Could somebody explain Q13 a-d in detail, and why currents do flow in some situations and doesn't in others: http://www.physics.ox.ac.uk/admissions/physicssample.pdf

Thanks in advance :smile:

Reply 1

teachercol

Resistor lets current flow either way

Diode only lets current flow one way only

Capacitor wont let a steady current flow in either direction.

When you connect the battery and meter, there are two routes the current might flow.

Reply 2

Omni

So: A-B resistor, B-C diode, C-A capacitor?
Capacitor = No current flows at all? (I thought capacitors had approx. normal current at first and then when time goes towards infinity the current goes towards zero)

Reply 3

teachercol

Effectively they dont allow a steady current to flow. There is a small current that decays exponentially. Here it will decay so fast as to reach zero very rapidly. Time constant = CR but R is very small