Explain why a voltmeter must have very high resistance?

Explain why an ammeter must have a low resistance .

Figure shows a potentiometer with a cell of 2.0 V and internal resistance 0.40 Omega maintaining a potential drop across the resistor wire AB. A standard cell which maintains a constant emf of 1.02V (for very moderate currents upto a few mA) gives a balance point at 67.3 cm length of the wire.To ensure that very low current drawn from the standard cell,a very high resistance of 600 k Omega is put in series with it, which is shorted close to the balance point. The standard cell is then replaced by a cell of unknown emf E and the balance point found similarly,turns out to be at 82.3 cm length of the wire . What purpose does the high resistance of 600 k Omega have?

True or False. Those substances which have extremely high resistance are called insulators.

Give reasons : Explain why rails have gaps at specific distances .

An ammeter should have very low resistance, so that it may

Explain why is modulation needed.

The series combination of galvanometer and high resistance is called as

A moving coil galvanometer of resistance 40 Omega gives full scales deflection when a current of 0.25 mA is paased through it. To convert it to voltmeter of range 10 V, the resistance requried to be placed in series is

Heat energy is being produced in a resistance in a cricuit at the rate of 100 W.The current of 3 A is flowing in the circuit.What must be the value of the resistance?

Name the following Substances having very low resistance