Electric current and its Effect
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Electric current and its Effect
Key Words
Electric current: The flow of electric charge through a conductor.
Electric circuit: The path through which an electric current can flow.
Battery: The connection of two or more cells in series or parallel.
Resistance: The property of a material through which it opposes the flow of current.
CFLs: Compact Fluorescent Lamps.
Electric fuse: Safety device which prevents excessive current from flowing in a circuit.
Short circuit: A sudden flow of very large current due to direct contact of a live wire and a neutral wire.
Overloading: The overheating of an electrical wiring in a circuit due to the flow of large
current through it.
MCB: Miniature circuit breaker.
Electromagnet: Electromagnets are temporary magnets consisting of a cylindrical coil (solenoid) around a soft iron bar as the core.
POINTS TO REMEMBER:
• Electric current is simply the flow of electric charge through a conductor.
• A cell is a source of electric current.
• Electric current is the source of all magnetic phenomena.
• Any closed path along which electric current or current carrying charge can flow is called an electric circuit.
• The heat energy produced in a conducting wire due to the flow of an electric current is known as the heating effect of an electric current.
• The amount of heat produced depends on the magnitude of the current, the time for which the current is passed, and the nature of the material of the wire.
• The electric bulb has a very thin, high-resistance filament made of Tungsten metal.
• CFL does not work on the heating effect of current. They do not have a filament and hence they do not waste electricity.
• A fuse is a safety device that prevents excessive current from flowing in a circuit. It works on the principle of the heating effect of electric current.
• The overheating of electrical wiring in any circuit due to the flow of a large current through it, (as too many electrical appliances are connected to a single socket) is called overloading of the electrical circuit.
• MCB is a special kind of an electrical switch which automatically turns off when the current in a circuit exceeds the safe limit. It works on the principle of the magnetic effect of an electric current.
• When an electric current passes through a wire, the current carrying wire behaves like a magnet by producing a magnetic field around it. This is called the magnetic effect of electric current.
• A solenoid is a cylindrical coil of tightly wrapped insulated conducting wire.
• Electromagnets are temporary magnets consisting of a cylindrical coil (solenoid) around a soft-iron bar (a magnetic material) as a core.
• An electric bell works on the principle of an electromagnet. It is used as a doorbell.
Exercises on Electric current and its Effect
Multiple Choice Questions (MCQs)
1. The filament of an electric bulb is made
of a thin wire of:
(a) copper
(b) aluminium
(c) nichrome
(d) tungsten
2. An electric fuse works on the:
(a) Chemical effect of current
(b) magnetic effect of current.
(c) lightning effect of current
(d) heating effect of current.
3. Nichrome wire is used in:
(a) CFL
(b) Electric Fuse
(c) Hair Dryer
(d) MCB
4. In a filament type bulb a lot of electric
energy is wasted in the form of:
(a) magnetism
(b) sound
(c) light
(d) heat
5. Which of these do not use the heating
effect of current?
(a) water heater
(b) electric bell
(c) electric iron
(d) electric kettle
6. The magnetic effect of electric current
was discovered by?
(a) Maxwell
(b) Darwin
(c) Oersted
(d) Newton
7. Which of the following characteristics is
not suitable for a fuse wire?
(a) thin and short
(b) thick and short
(c) low melting point
(d) higher resistance than rest of wiring.
Answers:
Multiple Choice Questions (MCQs)
1. (d) 2. (d) 3. (b) 4. (d) 5. (b) 6. (c) 7. (b)
Fill in the blanks:
1. Electric current is simply the flow of electric————– through a conductor.
2. The long line in the symbol for a cell represents its———– terminal.
3. The combination of two or more cells is called————-.
4. The safety device based on the heating effect of electric current is————-.
5. The magnet made by using electric current is called a/an—————-.
Answers:
Fill in the blanks:
1. Electric current is simply the flow of electric charge through a conductor.
2. The long line in the symbol for a cell represents its positive terminal.
3. The combination of two or more cells is called a battery.
4. The safety device based on the heating effect of electric current is fuse wire.
5. The magnet made by using electric current is called an electromagnet.