10.4+ 10.5 internal resistance +potential dividers Flashcards
what is electric potential energy?
what is internal resistance?
resistance due to the opposition of flow of charge within a source of e.m.f (cell)
represented as lowercase r
what is terminal p.d/ terminal voltage ?
the potenetial difference measured across the cell when the cell is connecetd by a complete circuit to a load (external resistance) . If there is no internal resistance p.d= ε emf
what are “lost volts”?
the difference between the terminal voltage and the e.m.f of a cell due to energy being dissipated across the ineternal resistance of the cell
what are the two equations for r?
what is external resistance?
combimed resistance of all components in the circuit (other than the power source)
represnted as capital R
what is the effect of total internal resistance ?
-
without: the coulomb of charge passing through a battery will have an increase in energy equal to the emf
eg: if emf is 12v then the coulumb of charge will gain 12j of electric potential energy when passing through - with: the coulomb of charge has to do work on the battery, so loses some of the energy
- eg: if emf is 12v, then may only gain 11.5j of electric potential energy as 0.5 lost to internal resistance
how would you measure emf and terminal voltage?
- emf: voltmeter in parallel with battery unconnected to rest of circuit
- terminal volatge: in parallel with battery connected to rest of circuit
in what cases does the emf = terminal volatge?
- internal resistance= 0
- power source not connected to external load
why is a smaller current favoured?
a smaller current will decrease the lost voltas and increase the terminal voltage
how would you determine r?
- record values of terminal voltage with varying current
- plot graph
- gradient =-r
- y intercept = ε
what is a poteniometer?
A potential divider circuit which consists of one length of wire and a sliding connection to alter the ratios resistances of the two sections of wire
what happens to the total resistance and current if the temperature is increased?
what is a potential divider?
A circuit which allows a user to vary an output potential difference using the principle of shared potential differences given by Kirchhoff’s Second Law
Why happens to V out as the contact is moved towards A and B?
As moves towards A, V out increases until = V in
As moves towards B, V in decreases until =0
Potential divider
Internal resistance Q
