Class 10 Science Chapter 12 Question Answers - Magnetic Effects of Electric Current

Q1: What does the direction of thumb indicate in the right-hand thumb rule? In what ways this rule is different from Fleming’s left-hand rule?
Ans: The thumb indicates the direction of current in the straight conductor held by curled fingers, whereas Fleming’s left-hand rule gives the direction of force experienced by current carrying conductor placed in an external magnetic field.

Q2: What is the difference between a direct current and an alternating current? How many times does AC used in India change direction in one second?
Ans: Direct current always flows in one direction but the alternating current reverses its direction periodically. The frequency of AC in India is 50 Hz and in each cycle it alters direction twice. Therefore, AC changes direction 2 × 50 = 100 times in one second.

Q3: What is the role of fuse, used in series with any electrical appliance? Why should a fuse with defined rating not be replaced by one with larger rating?
Ans: Fuse is used for protecting appliances due to short-circuiting or overloading. The fuse is rated for a certain maximum current and blows off when a current more than the rated value flows through it. If a fuse is replaced by one with larger ratings, the appliances may get damaged while the protecting fuse does not burn off. This practice of using fuse of improper rating should always be avoided.

Q4: On which factors does the magnetic field produced by a current carrying conductor at a given point depend?
Ans:

• The magnetic field produced by a given current decreases as the distance from it increases.
• The magnitude of the magnetic field produced at a given point increases as the current through the wire increases.

Q5: What is electric generator? Write down its principle of working.
Ans: Electric Generator: A generator converts mechanical energy into electrical energy.
Principle: It works on the basis of electromagnetic induction. AC generator produces AC current and DC generator produces DC current.

Q6: What is difference between AC and DC? Write down advantage of AC over DC?
Ans: The difference between the direct and alternating currents is that the direct current always flows in one direction, whereas the alternating current reverses its direction periodically.
In India, the AC changes direction after every 1/100 second, that is, the frequency of AC is 50 Hz. An important advantage of AC over DC is that electric power can be transmitted over long distances without much loss of energy.

Q7: What is electric motor? Write down its principle of working.
Ans: Electric motor: An electric motor is a rotating device that converts electrical energy to mechanical energy.
Principle: A current-carrying conductor when placed in a magnetic field experiences a force.

Q8: What is galvanometer?
Ans:

• A galvanometer is an instrument that can detect the presence of a current in a circuit.
• The pointer remains at zero (the centre of the scale) for zero current flowing through it.
• It can deflect either to the left or to the right of the zero mark depending on the direction of current.

Q9: Describe domestic electric circuits.
Ans: Domestic Electric circuits: In our houses, we receive AC electric power of 220 V with a frequency of 50 Hz. One of the wires in this supply is with red insulation, called live wire. The other one is of black insulation, which is a neutral wire. The potential difference between the two is 220 V.
The third is the earth wire that has green insulation and this is connected to a metallic body deep inside the earth. It is used as a safety measure to ensure that any leakage of current to a metallic body of an appliance does not give any severe shock to the user.

Q10: What will happen if a current carrying conductor is placed in magnetic field? How can the direction of magnetic field be found out?
Ans: A current-carrying conductor when placed in a magnetic field experiences a force.
If the direction of the field and that of the current are mutually perpendicular to each other, then the force acting on the conductor will be perpendicular to both as given by Fleming’s left-hand rule.