Electrical Circuits

Question 1

What is a potential divider circuit? Give the formula

Answer 1

A simple circuit that uses resistors (thermistors/LDRs) to provide a variable potential difference

V1= (R1/R1+R2)x V(in)

Question 2

How is the resistance in a potential divider circuit related to the potential difference?

Answer 2

Resistance is directly proportional to potential difference and the ratio of a resistor R1 to the total resistance is equal to the ratio of the voltage V1 (to the total voltage ) over resistor R1

Question 3

What is a short circuit?

Answer 3

When there is no load (external components) so the resistance is 0.
The battery delivers the maximum possible current:
E/r
r - internal resistance of battery

Question 4

Why does a cell get hot?

Answer 4

-Work is done by the charges as they move through the power supply and energy is transferred by heating
-When connected to an external circuit, some energy is lost within the power source, this causes the p.d. at the terminals to be less than the EMF

Question 5

Define potential difference and electromotive force

Answer 5

Potential difference - Work done by charge carriers which lose energy as they move through the components
EMF - Work done on charge carriers which gain energy as they pass through a power supply

Question 6

What is the formula to calculate EMF?

Answer 6

EMF = terminal p.d. + lost volts

EMF = I(R+r)
I - current / A
R - Resistance across circuit
r - Internal resistance