2010 Q25 (a) (ii)

Found the answers online but still don't understand. Was wondering if you could explain this

Calculate the reading on the voltmeter when R1=1600 R2= 6000 R3= 800 R4=4000 12v supply

Thanks

Chris,
A voltmeter measures the difference in potential between the two inputs, in this case the difference between point P and point Q.
To find the voltage at P you need to find the voltage dropped across the 800 ohm resistor;
Vp = (12 * 800) / (800 + 1600). Vp = 4V
To find the voltage at Q you need to find the voltage dropped across the 4000 ohm resistor;
Vq = (12 * 4000) / (4000 + 6000). Vq = 4.8V

The reading on voltmeter = 4.8 - 4 = 0.8V.

Dows this explain it now Chris.

Yeh, makes sence now. thanks