Hey!
I have this little problem with calculating the reading on a voltmeter when it has internal resistance.
Say you have a 500Ohms and a 2000Ohms resistors placed in series with a 60V supply, and there is a voltmeter with internal resistance of 2000Ohms being used to read the PD across each. What would be the reading on the voltmeter when a) placed across the 500Ohm resistor and b) placed across the 2000Ohm resistor?
My first instinct is to use V = IR. R (total) being 2000 + 2000 + 500 = 4500, so I = 60/4500. Then I would say that V = (60/4500) * 500 for the 500ohm resistor. This gives 20/3V. Then to account for the lost volts I would say V = (60/4500) * 2000 which gives 80/3V. I then would do 20/3 - 80/3, but this gives 20V and the answer sheet says 10V.
What have I done wrong?