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Practice each question, then open the answer or worked solution.
Which of the following correctly describes the magnetic field near a long straight wire?
4. The field consists of concentric circles centred on the wire.
The magnetic field near a long straight wire is concentric circles. Their centres lie on the wire.
The phenomenon of electromagnetic induction is
3. producing induced current in a coil due to relative motion between a magnet and the coil.
The phenomenon of inducing current in a coil due to the relative motion between the coil and the magnet is known as electromagnetic induction.
The device used for producing electric current is called a
a. generator
The device used for producing electric current is known as a generator. The generator converts mechanical energy to electric energy.
The essential difference between an AC generator and a DC generator is that
4. AC generator has slip rings, while the DC generator has a commutator.
AC generators have two rings known as the slip rings, while DC generators have two half rings known as the commutator. This is the main difference between AC generator and DC generator.
At the time of short circuit, the current in the circuit
3. increases heavily
When two naked wires in the circuit come in contact with each other, the amount of current flowing in the circuit increase abruptly resulting in short circuit.
State whether the following statements are true or false.
1. False
An electric motor converts electrical energy into mechanical energy.
2. True
An electric generator is a device that generates electricity by rotating a coil in a magnetic field.
3. True
A long circular coil is a solenoid. The magnetic field lines inside a solenoid are parallel straight lines.
4. False
Live wires have red insulation cover, while the earth wire has green insulation.
List two methods of producing magnetic fields.
Following are the methods of producing magnetic fields:
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.
A solenoid is a long coil of circular loops of insulated copper wire. The magnetic field produced around the solenoid when the current is passed through it is similar to the magnetic field produced around the bar magnet when a current is passed through it. The figure shown below shows the arrangement of magnetic fields produced around the solenoid when current is passed through it.
When the north pole of the bar magnet is brought close to the end connected to the negative terminal of the battery, the solenoid repels the battery. As like poles repel each other, we can infer that the end connected to the negative terminal behaves as a north pole while the end connected to the positive terminal behaves as a south pole.
When is the force experienced by a current–carrying conductor placed in a magnetic field largest?
When the direction of the current is perpendicular to the direction of the magnetic field, the force experienced is the largest.
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?
The direction of the magnetic field can be determined using Fleming’s Left-hand rule. The direction of the magnetic field will be perpendicular to the direction of the current and the direction of deflection, i.e., either upward or downward. The direction of the current is from the front wall to the back wall because negatively charged electrons move from the back wall to the front wall. The direction of the magnetic force is rightward. Hence, using Fleming’s left-hand rule, it can be concluded that the direction of the magnetic field inside the chamber is downward.