Electromagnet and Its Application

A short solenoid (length $L$ and radius $r$, with $n$ turns per unit length) lies well inside and on the axis of a very long, coaxial solenoid (radius $R$ and $N$ turns per unit length, with $R>r$ ). Current $I$ flows in the short solenoid. Choose the correct statement.

The magnetic field inside a long straight current carrying solenoid :

The magnetic field inside a solenoid is

Which of the following is most suitable for the core of electromagnets?

What must happen for an electromagnet to have a magnetic field?

If the direction of current in a solenoid, when viewed from a particular end, is anticlockwise, then the other end of the solenoid will be:

A short solenoid (length $l$ and radius $r$ with $n$ turns per unit length) lies well inside and on the axis of a very long, coaxial solenoid (length $L$, radius $R$ and $N$ turns per unit length, with $R>r$). Current $I$ follows in the short solenoid. Choose the correct statement.

When electric current is passed through the solenoid, it shows magnetic lines of force similar to a _____.

For a current in a long straight solenoid N-pole and S-pole are created at the two ends. Among the following statements, the incorrect statement is

Two current-carrying solenoids exhibit: 

Four metal rods are placed, in turn, inside a coil of copper wire.

The table below gives the results of the experiment. Which rod would be the most suitable to use for the case of a coil in a circuit breaker?

The material of the core of a strong electromagnet is:

If we insert a steel rod inside the coil of an electromagnet, 

The expression for magnetic induction inside a solenoid of length $L,$ carrying a current $i$and having $N$ number of turns are