AS Physics question: wts the diff. between EMF and PD?

So due to conservation of energy, EMF = PD?

Reply 5

figgetyfig

2

As far as the AS exam is concerned, just assume that they are the same.

EMF is what drives current. PD is the potential energy per unit charge.

Reply 6

So the difference between them is the energy lost in the circuit?

Reply 7

elpaw

15

EMF is the voltage supplied by an active component (battery, dynamo, etc). PD is the voltage accross a passive component (resistor, capacitor, etc).

Reply 8

So can you say the PD across a battery with EMF 5V is 5V?

Reply 9

elpaw

15

mik1a

So can you say the PD across a battery with EMF 5V is 5V?

if you disregard internal resistence (i.e. the current through the battery is 0A), yes.

Reply 10

imasillynarb

I dont think this is correct?

Well then you're a silly narb!

EMF is the amount of energy stored in the battery converted to electrical energy per unit charge passing through the battery.

P.D. is the amount of electrical energy per unit of charge converted to other forms of energy in while passing through a component.

Reply 11

So the difference between the two is equal to the internal resistance?

Reply 12

mik1a

So the difference between the two is equal to the internal resistance?

Not equall to, but determined by.

Reply 13

Not equal to?

Reply 14

mik1a

Not equal to?

Here's an example:

EMF of battery: 5V

Internal resistance: 0.5ohms

Current: 2A

Then the voltage lost through internal resistance (V= IR) = 1V

So if you have a component on the circuit, pd = 4V

I think :rolleyes:

Reply 15

hitchhiker_13

Here's an example:

EMF of battery: 5V

Internal resistance: 0.5ohms

Current: 2A

Then the voltage lost through internal resistance (V= IR) = 1V

So if you have a component on the circuit, pd = 4V

I think :rolleyes:

Ok thankyou very much, I never understood internal resistance. Now I have an idea at least.

Reply 16