Magnetic Effects of Electric Current quiz

Magnetic field lines emerge from the:

Inside a long straight current-carrying solenoid, the magnetic field:

The direction of the magnetic field around a straight current-carrying conductor is given by the:

The force on a current-carrying conductor in a magnetic field is maximum when the angle between the current and the field is:

The frequency of AC supply in India is:

The colour of insulation of the earth wire in domestic circuits is usually:

A soft iron core placed inside a solenoid:

Which of the following properties of a proton can change while it moves freely in a magnetic field?

The potential difference between the live wire and the neutral wire in Indian homes is:

Which device protects an electric circuit from overloading by melting?

Why does a compass needle get deflected when brought near a bar magnet? (2 marks)

Why don't two magnetic field lines intersect each other? (2 marks)

Consider a circular loop of wire lying in the plane of the table. Let the current pass through the loop clockwise. Apply the right-hand rule to find the direction of the magnetic field inside and outside the loop. (2 marks)

The magnetic field in a given region is uniform. Draw a diagram to represent it. (2 marks)

What does the closeness of magnetic field lines near the poles of a magnet indicate? (2 marks)

List two methods of producing magnetic fields. (2 marks)

How does a solenoid behave like a magnet? Can you determine the north and south poles of a current-carrying solenoid with the help of a bar magnet? Explain. (2 marks)

When is the force experienced by a current-carrying conductor placed in a magnetic field the largest? (2 marks)

Name two safety measures commonly used in electric circuits and appliances. (2 marks)

What precaution should be taken to avoid the overloading of domestic electric circuits? (2 marks)

In a home, the main fuse is rated 25 A on a 220 V supply. Find the maximum power that can be drawn safely. How many 1.5 kW air conditioners could run together without blowing the fuse, if nothing else is switched on? (3 marks)

A 1000 W electric kettle and a 1500 W toaster are to be used in the kitchen on a 220 V line. Calculate the current drawn by each, and suggest a suitable fuse rating (5 A or 15 A) for each appliance circuit. Explain your choice. (3 marks)

An AC supply has a frequency of 50 Hz. Calculate (i) the time period (ii) the number of times the current becomes zero in one second (iii) the number of complete cycles in one minute. (3 marks)

A straight wire produces a magnetic field of strength B at a distance of 4 cm. At what distance will the field be B/2 if the current is unchanged? At what distance would the field be 2B? Use the fact that the field is inversely proportional to distance. (3 marks)

A student uses a solenoid of 400 turns carrying 2 A as an electromagnet. She needs a field twice as strong but can only supply 1 A. How many turns must her new solenoid of the same length have? Explain your reasoning. (3 marks)

Read the passage and answer the questions. Rahul's family noticed that whenever the geyser, the electric iron and the room heater were switched on together, the main fuse of their house melted. An electrician told them the circuit was being overloaded. (i) What is overloading? (ii) Why does the fuse melt in such a situation? (iii) Suggest two ways to prevent overloading. (5 marks)

Read the passage and answer the questions. A student places a compass needle at various points around a long straight wire carrying a current vertically upward through a horizontal cardboard sheet. She sprinkles iron filings on the sheet and taps it gently. (i) What pattern do the iron filings form? (ii) What happens to the deflection of the compass when the current is increased? (iii) What happens to the direction of the compass needle when the direction of the current is reversed? (5 marks)

Read the passage and answer the questions. An electric iron with a metal body is connected to a three-pin plug. One day, due to a fault, the live wire inside touches the metal body. Because the iron is properly earthed, the user does not get a shock and the fuse blows. (i) What is the role of the earth wire here? (ii) Why did the fuse blow? (iii) Why is the earth wire not needed for appliances with plastic bodies? (5 marks)

Read the passage and answer the questions. Electromagnets are used in cranes to lift heavy iron scrap in junkyards. They are made by winding many turns of insulated copper wire around a soft iron core. (i) Why is soft iron used for the core and not steel? (ii) How can the strength of an electromagnet be increased? Give two ways. (iii) Why is an electromagnet more useful than a permanent magnet in a crane? (5 marks)

Read the passage and answer the questions. Electric power in India is supplied as alternating current at 220 V and 50 Hz. Some devices, such as mobile phones and laptops, work on direct current and use adaptors. (i) Differentiate between AC and DC. (ii) What is the frequency of AC in India and what does it mean? (iii) State one important advantage of AC over DC for transmission over long distances. (5 marks)

Describe an activity to show that a current-carrying straight conductor produces a magnetic field around it. Draw a labelled diagram showing the pattern of field lines and their direction. How does the field change with (i) an increase in current (ii) an increase in distance from the wire? State the rule used to find the direction of the field. (6 marks)

Draw the pattern of magnetic field lines produced by a current-carrying circular loop, and explain why the field lines near the centre are nearly straight. How does the magnetic field at the centre depend on the current, the radius and the number of turns? Explain with diagrams. (6 marks)

What is a solenoid? Draw the field lines inside and around a current-carrying solenoid and compare them with those of a bar magnet. Explain how a strong magnetic field inside a solenoid can be used to magnetise a piece of soft iron, and list two differences between an electromagnet and a permanent magnet. (6 marks)

State Fleming's left-hand rule and draw a diagram showing the directions of field, current and force. Describe an experiment with a labelled diagram to show that a current-carrying conductor experiences a force in a magnetic field, and state two devices that use this effect. (6 marks)

Draw a schematic diagram of a common domestic circuit showing the main supply, electricity meter, distribution box with fuses, live, neutral and earth wires, and separate circuits for 15 A and 5 A appliances. Explain the role of each wire, the fuse and the earthing. Why are appliances connected in parallel? (6 marks)