I'm trying to understand e.m.f. with cells and wondered if the following diagrams are correct or not:
Do the voltages just add or subtract together to give a resultant voltage as I've drawn?
Thanks for any help.
yeah - though I'd draw it a bit differently
FWIW this shows Kirchoffs Voltage law - that the sum of all pd's around a loop is zero.
you can decide to say clockwise is negative and go around the loop adding up -3 +9 -6 equals 0 (you could equally validly pick any any start/end point or order)
and obviously you'd get the same result if you decided clockwise was positive.
it's useful if you know some of the pd's in a loop - because the unknown pds have to add up with the known pds to give a total of zero around the loop.
Is the second circuit diagram basically how a battery charger works? You have a bigger voltage reversing the current flow to charge the smaller battery?
Is the second circuit diagram basically how a battery charger works? You have a bigger voltage reversing the current flow to charge the smaller battery?
Well the basic idea there is to force charge back into the battery you're recharging with a reverse current... seeing opposing batteries doesn't imply one of the batteries is getting charged though, it might not be a rechargable type in which case it's just passing current and getting hot.
The X point would attach to the positive terminal of the battery and the Y to the negative terminal. Thus producing a 'backwards' flow through the battery.
The X point would attach to the positive terminal of the battery and the Y to the negative terminal. Thus producing a 'backwards' flow through the battery.
yeah so if you're jump starting a car you put the leads +ve to +ve and -ve to -ve