2.3 D.C. Circuits

what is conserved in parallel circuits?

charge

in parallel circuits the … is the sum of the branches and the … is equal in all branches

current, potential difference

what is conserved in a series circuit?

energy

in series circuits the … is the sum of the branches and the … is equal in all branches

potential difference, current

in series resistors…

add up

how do you combine resistors in a parallel circuit?

you take the reciprocal of the sum of the reciprocals

what are potential dividers?

circuits which aim to deliberately divide the potential difference from a source to two or more components

what is the share potential difference given to a component by a potential divider based on?

resistance

what can LDRs and thermistors be used for in a potential divider circuit?

to alter the output of a device

what happens to a thermistor as the temperature of the surroundings rise?

the resistance falls and the pd also falls

what happens to an LDR as light intensity increases?

the resistance decreased therefore the pd across it decreases

what does emf stand for?

electromotive force

what is emf?

the energy supplied per unit charge in a circuit from the source to produce the potential difference

how can you model the energy lost across the internal resistance of the source?

as a fixed resistor of resistance (r )

what can you do when cells are in series?

add up the emf and add up the internal resistance to make one cell