Why is a resistance connected in series with a zener diode when used in a circuit?

A zener diode is used as

Zener diode is used for:

Aseries resistance is connected is the zener diode circuit to:

State the uses of resistance connected in series with the galvanometer.

A range of galvanometer is V, when 50Omega resistance is connected in series. Its range gets doubled when 500Omega resistance is connected in series. Galvanometer resistance is

If three resistors 15Omega , 3Omega and 4 Omega each are connected in series, what is the effective resistance in the circuit?

Three resistors having resistances of 15 Omega , 3 Omega and 4 Omega are connected in series. What is the effective resistance in the circuit?

When a resistance of 100Omega is connected in series with a galvanometeer of resistance R, its range is V. To double its range, a resistance of 1000Omega is connected in series. Find R.

Three resistors having resistances of 12 Omega , 9 Omega , 4 Omega and 3 Omega are connected in series. What is the effective resistance in the circuit?

Choose the correct alternative. If three resistors, having values 2 ohm, 3 ohm and 4 ohm are connected in series, then effective resistance in a circuit will be ______ohm.