--- title: "NCERT Solutions Class 10 Science Ch 12 Ex EXERCISES" url: https://www.swavid.com/science/class/10/chapter/magnetic-effects-of-electric-current/ncert-solutions/exercise-exercises dateModified: 2026-10-07T16:47:25+00:00 --- # NCERT Solutions Class 10 Science Ch 12 Ex EXERCISES Chapter 12: Magnetic Effects of Electric Current. Every question from Exercise EXERCISES, with full working and the final answer. Free PDF (11 pages): https://www.swavid.com/api/seo/pdf/ncert/science/class-10/swavid-ncert-solutions-class-10-science-chapter-12-magnetic-effects-of-electric-current-5cc5cb02b7.pdf ## EXERCISES ### Question 1 *1 mark · MCQ* Which of the following correctly describes the magnetic field near a long straight wire? - The field consists of straight lines perpendicular to the wire. - The field consists of straight lines parallel to the wire. - The field consists of radial lines originating from the wire. - The field consists of concentric circles centred on the wire. **Solution** 1. The magnetic field lines around a current-carrying straight wire consist of a series of concentric circles. 2. Therefore, option (d) is the correct description. **Answer:** (d) The field consists of concentric circles centred on the wire. > Common mistake: Confusing concentric circles with radial or parallel lines. ### Question 2 *1 mark · MCQ* At the time of short circuit, the current in the circuit - reduces substantially. - does not change. - increases heavily. - vary continuously. **Solution** 1. When the live wire and the neutral wire come into direct contact, a short circuit occurs. 2. In this situation, the current in the circuit abruptly increases heavily. **Answer:** (c) increases heavily. > Common mistake: Thinking that current decreases during a short circuit. ### Question 3 *2 marks · True or false* State whether the following statements are true or false. (a) The field at the centre of a long circular coil carrying current will be parallel straight lines. (b) A wire with a green insulation is usually the live wire of an electric supply. **Part (a)** 1. At the centre of a circular loop carrying current, the arcs of the concentric circles appear as straight lines. Answer (a): True **Part (b)** 1. A wire with green insulation is used as the earth wire for safety, while the live wire has red insulation. Answer (b): False **Answer:** (a) True, (b) False > Common mistake: Confusing the color coding of live and earth wires in domestic circuits. ### Question 4 *2 marks · Very short answer* List two methods of producing magnetic fields. **Solution** 1. A magnetic field can be produced by using a permanent magnet. 2. A magnetic field can also be produced by passing an electric current through a conductor, such as a straight wire, a circular loop, or a solenoid. **Answer:** Two methods of producing magnetic fields are by using a permanent magnet and by using a current-carrying conductor. > Common mistake: Listing appliances instead of the underlying physical methods. ### Question 5 *2 marks · Very short answer* When is the force experienced by a current-carrying conductor placed in a magnetic field largest? **Solution** 1. The force experienced by a current-carrying conductor placed in a magnetic field depends on the angle between the direction of current and the magnetic field. 2. The magnitude of the force is highest when the direction of current is at right angles to the direction of the magnetic field. **Answer:** The force is largest when the direction of current is at right angles to the direction of the magnetic field. > Common mistake: Stating parallel instead of perpendicular. ### Question 6 *3 marks · Short answer* Imagine that you are sitting in a chamber with your back to one wall. An electron beam, moving horizontally from back wall towards the front wall, is deflected by a strong magnetic field to your right side. What is the direction of magnetic field? **Solution** 1. The electron beam moves from the back wall to the front wall, which means the conventional current flows in the opposite direction, from the front wall to the back wall. 2. The deflection of the electron beam is to the right side of the observer, which represents the direction of the force acting on the electron. 3. Applying Fleming's left-hand rule, with the second finger pointing towards the back wall (direction of current) and the thumb pointing to the right (direction of force), the forefinger points vertically downwards. **Answer:** The direction of the magnetic field is vertically downwards. > Common mistake: Taking the direction of electric current to be the same as the direction of motion of electrons, instead of taking it opposite. ### Question 7 *4 marks · Case-based* State the rule to determine the direction of a (i) magnetic field produced around a straight conductor-carrying current, (ii) force experienced by a current-carrying straight conductor placed in a magnetic field which is perpendicular to it, and (iii) current induced in a coil due to its rotation in a magnetic field. **Part (i)** 1. Imagine holding a current-carrying straight conductor in your right hand such that your thumb points in the direction of current. 2. Your fingers will wrap around the conductor in the direction of the magnetic field lines. Answer (i): Right-hand thumb rule **Part (ii)** 1. Stretch the thumb, forefinger, and middle finger of your left hand such that they are mutually perpendicular. 2. If the first finger points in the direction of magnetic field and the second finger in the direction of current, then the thumb points in the direction of force. Answer (ii): Fleming's left-hand rule **Part (iii)** 1. Stretch the thumb, forefinger, and middle finger of your right hand to be mutually perpendicular. 2. If the forefinger points in the direction of magnetic field and the thumb points in the direction of motion of the conductor, then the middle finger points in the direction of induced current. Answer (iii): Fleming's right-hand rule **Answer:** Right-hand thumb rule, Fleming's left-hand rule, and Fleming's right-hand rule. > Common mistake: Mixing up left-hand and right-hand rules for force and induced current. ### Question 8 *2 marks · Very short answer* When does an electric short circuit occur? **Solution** 1. An electric short circuit occurs when the live wire and the neutral wire come into direct contact. 2. This happens due to damage in the insulation of wires or a fault in the appliance, causing the current in the circuit to abruptly increase. **Answer:** A short circuit occurs when the live wire and neutral wire come into direct contact due to damaged insulation or a fault. > Common mistake: Confusing short-circuiting with overloading due to connecting too many appliances. ### Question 9 *3 marks · Short answer* What is the function of an earth wire? Why is it necessary to earth metallic appliances? **Solution** 1. The earth wire has green insulation and is connected to a metal plate deep in the earth near the house. 2. Its function is to provide a low-resistance conducting path for any leakage of current from the metallic body of an appliance. 3. It is necessary to earth metallic appliances so that any accidental current leakage keeps the potential of the appliance to that of the earth, protecting the user from a severe electric shock. **Answer:** Earth wire provides a safe low-resistance path to the ground for leaked current, preventing severe electric shocks from metallic appliances. > Common mistake: Stating that the earth wire carries regular operating current instead of leakage current. ## Related pages - [All Chapter 12 NCERT solutions](https://www.swavid.com/science/class/10/chapter/magnetic-effects-of-electric-current/ncert-solutions) Solutions written by SwaVid, a personal AI tutor for Class 6 to 10 Maths and Science. Practise this chapter free: https://www.swavid.com/start/student