C-12 — Magnetic Effects of Current

Which of the following materials is attracted by a magnet?

How many poles does a magnet have?

What happens when two similar poles of magnets are brought close?

What happens when two dissimilar poles of magnets are brought close?

A bar magnet suspended freely points along which direction?

The pole of a freely suspended magnet that points towards the geographic north is called —

Why does a freely suspended magnet always align in the north-south direction?

Around a stationary electric charge, which field is produced?

Around a current-carrying wire, which field is produced?

The shape of magnetic lines of force around a long straight current-carrying wire is —

When current through a wire is stopped, the surrounding compasses —

If the direction of current through a wire is reversed, the direction of the magnetic field —

According to the right hand rule for a straight wire, the thumb indicates —

According to the right hand rule for a straight wire, the other fingers indicate —

A solenoid is —

Why is a solenoid (many-turn coil) used to produce a strong magnetic field instead of a single loop?

The heat dissipated in a current-carrying wire is proportional to —

A current-carrying solenoid behaves like —

According to the right hand rule for a circular coil, the thumb shows —

In a current-carrying solenoid, the direction in which the thumb points (right-hand rule) is the —

Inserting a piece of iron inside a current-carrying solenoid —

The three metals with special magnetic properties are —

Why does an ordinary piece of iron not act as a magnet?

When current flows through a solenoid containing an iron core, the tiny magnets inside the iron —

When the current in an electromagnet is switched off —

A magnet prepared by passing current through a solenoid wrapped around an iron core is called —

Electromagnets are used in —

In a speaker, the electromagnet vibrates —

When a current-carrying wire is placed in an external magnetic field, it —

The force on the wire arises because —

If the direction of current through the wire is reversed, the direction of force on it —

A DC motor converts —

The function of the commutator in a DC motor is —

Without a commutator, the rotating coil of a motor would —

When the commutator terminals lose contact with the brushes, the coil keeps rotating due to —

Consider the following statements about a DC motor:

The voltage produced in a coil due to a changing magnetic field through it is called —

The current produced in a coil due to a changing magnetic field is called —

When a bar magnet is suddenly inserted into a coil connected to an ammeter —

When the bar magnet is pulled out of the coil, the induced current —

If a strong magnet is held stationary inside a coil, then —

For an induced current to flow in a coil, the magnetic field through it must —

The phenomenon of generation of voltage and current in a coil due to a changing magnetic field is called —

A generator converts —

If the armature of a DC motor is rotated mechanically (with an ammeter connected instead of a battery), the current obtained is —

If an AC motor is rotated mechanically as a generator, the current obtained is —

In a transformer, electrical energy is transferred from one coil to another —

The coil of a transformer to which AC voltage is applied is called the —

The coil of a transformer from which the output voltage is taken is called the —

The voltage and turns relation in an ideal transformer is —

A step-up transformer has —

A step-down transformer has —

In an ideal transformer, the relation between primary and secondary quantities is —

If a transformer increases the voltage by 10 times in the secondary, the current in the secondary becomes —

For long-distance transmission of electricity, the type of transformer used at the generation station is —

In a transformer with $N_p = 100$ and $N_s = 1000$, if 10 V DC is applied to the primary, the voltage across the secondary is —

A transformer does not work with DC because —

In a transformer with $N_p = 100$ and $N_s = 1000$, if 12 V AC is applied to the primary, the secondary voltage is —

In the transformer of the previous question, if 1 A current flows through the primary, the maximum current in the secondary is —

The wires of both coils in a transformer are covered with insulating material in order to —

Consider the following statements about an ideal transformer:

What will happen to the magnetic field if electric current flows through a solenoid made by insulated wire wound over a cylinder?

In which of the following functions is electromagnetic induction used?

In which of the following processes is electromotive force produced —

In a transformer, primary voltage is 200 V, secondary voltage is 800 V and number of turns in the primary coil $n_p = 100$. What is the value of $n_s$?

According to the stem of the previous question (200 V primary, 800 V secondary) —

What is electromagnetism?

A long straight wire passes perpendicularly through a sheet of paper and current flows through it. Iron dust spread on the paper will arrange themselves —

To increase the intensity of the induced magnetic field of a current-carrying straight wire, the best change is —

If an insulated wire is wrapped around an iron nail and current is passed, the nail acts as —

The main difference between an electric motor and a generator is —

Why is AC voltage applied to the primary coil of a transformer?

Why are the wires on both sides of a transformer core covered with insulating material?

Why is a commutator used in an electric motor?