electric circuits

Mains supply in UK

50Hz

So current changes direction 100 times each second

And produces 50 cycles per second

Is water a conductor or insulator?

Conductor, unless extremely pure

VI graph of any ohmic conductor (fixed resistor eg)

Linear, going through origin, gradient = R

VI graph of filament lamp

Goes through origin, but temperature is not constant and increases so at a point, resistance increases creating a curve.

In this case, gradient is not consistent so to find R at any point, you divide V by I at that point.

NTC thermistor

As temperature increases, resistance decreases

LDR

As light intensity increases, resistance decreases

Flow in a circuit and diodes

Positive terminal → circuit → negative terminal

A diode looks like an arrow, the arrow should correspond to this flow, otherwise no current flows through

The temperature of the thermistor decreases. What happens to the readings 1 and 2?

Temp decreases therefore the resistance of the thermistor increases and so the overall resistance of the circuit increases.

This reduces the current in the circuit so the reading decreases is meter 1.

In the fixed resistor, since R is the same here but current has decreased, V has also decreased in the fixed resistor

So the thermistor gets a larger share of voltage, so reading on meter 2 increases