[填空题]
Three resistors with rh ,a h4bynwwz+s/+7f zes85tqot5 w4 hkxv b38x/ye; nwvistances $10\,Ω$,$20\,Ω$ and $30\,Ω$ are connected with two cells as shown.
The switch is in the open position shown, and both the ammeter and voltmeter are ideal.
1.State what is meant by electromotive force.
2.Determine the reading of the voltmeter. V= $V$
3.The]3.The]4.With the switch remaining closed, the ammeter is replaced with a non-ideal meter.
Determine how this affects the reading of the voltmeter. Justify your answer.
