Insert your ammeter in the circuit shown and measure the current. Now measure th
ID: 2078337 • Letter: I
Question
Insert your ammeter in the circuit shown and measure the current. Now measure the current with the standard ammeter. Compare these readings. Why is a voltmeter a high resistance instrument? Why is an ammeter a low resistance instrument? You are given an ammeter with a range of 0-3 A. You need an instrument with a range of 0-20 A. How would you proceed to make such a meter? A laboratory galvanometer shows a full scale deflection for a current of 2.00 mA. This 3.0-V voltmeter when connected in series same galvanometer can be used to make a with a 1.450 Ohm resistor, what resistance connected in series with this galvanometer will yield a 15.0-V voltmeter?Explanation / Answer
a) For measuring voltage we need to connect voltmeter in parallel combination. For the same we need to have a large resistance in order to make the total current passes through the circuit only.
b) For measuring current, we need to connect ammeter in series with circuit. For measuring the current through total circuit, the internal resistance of the ammeter should be very less. If the internal resistance is comparable to the circuit resistance then it alters the current passing through circuit so we cannot measure the actual current. So the internal resistance of ammeter is sholud be neglisible compared to the resistance of the circuit.