RBSE Solutions for Class 8 Science Chapter 11 Effects of Electric Current

RBSE Solutions for Class 8 Science Chapter 11 Effects of Electric Current are part of RBSE Solutions for Class 8 Science. Here we have given RBSE Rajasthan Board Solutions for Class 8 Science Chapter 11 Effects of Electric Current.

Rajasthan Board Solutions for Class 8 Science Chapter 11 Effects of Electric Current

Board	RBSE
Class	Class 8
Subject	Science
Chapter	Chapter 11
Chapter Name	Effects of Electric Current
Number of Questions Solved	40
Category	RBSE Solutions

Effects of Electric Current Textbook Questions Solved

I. Multiple Choice Questions

Question 1.

1. Electric bell is based on which electric current effect
   (a) Thermal effect
   (b) magnetic effect
   (c) chemical effects
   (d) joule effect
2. What is the object used to collect the magnetic matter from this scrape?
   (a) electric magnet
   (b) electric cell
   (c) fuse
   (d) Immersion rod
3. Which of the following solution not pass electric current?
   (a) Copper sulphate
   (b) Silver nitrate
   (c) Pure water
   (d) Salted water
4. Which is not a component of electric bell?
   (a) strip of iron
   (b) coil
   (c) contact nut
   (d) magnetic needle

Answers:

1. (b)
2. (a)
3. (d)
4. (d)

Question 2.
Fill in the blanks

1. The long line represents…………………and short line represents…………………terminal of electric battery’s symbol.
2. The safety device based on heating effect of electric is called…………………
3. In battery, the plate connected to the positive terminal is called…………………and to negative terminal is called
4. The magnetic effect of electric current is discovered by…………………

Answers:

1. Positive terminal, negative terminal
2. Fuse
3. Anode and Cathode
4. Aursted

Effects of Electric Current Short Answer Type Questions

Question 1.
What is fuse?
Answer:
Fuse is a safety device that off the electric current in a circuit if a sudden heavy current starts flowing in it.

Question 2.
Write any three applications of electromagnet.
Answer:
Application of Electromagnet:

1. To separate things from scrape.
2. Accidentally pieces of magnet fall in eyes are removed from eyes by an electric magnet.
3. Electric magnetic crane is used to lift heavy iron goods.

Question 3.
What is thermal effect of electric current? Write down the names of any four appliances based on this effect.
Answer:
Whenever an electric current flows through a conductor, some of it gets converted into heat energy. This is the heating effect of electric current. The greater the resistance offered by the wire to the flow of current, the greater would be the heat generated. That is why copper wires, which offer very little resistance, do not get heated up. Nichrome and tungsten offer high resistance to the flow of electric current and get heated up. Besides the material, the amount of heat generated in a wire also depends of the length and thickness of the wire. The heating effect of electric current is used in a large number of domestic and industrial appliances for example, room heater, electric kettle, geyser, toaster, electric iron, hair dryer, oven, etc.

Effects of Electric Current Long Answer Type Questions

Question 1.
Make a diagram of electric bell and explain its working system.
Answer:
The electric bell: Figure shows a simple electric bell. It consists of an electromagnet, an armature, a contact adjusting screw, A gong and hammer. The armature consists of a soft iron rod mounted on a spring. One end of the iron rod presses against the top of the contact adjusting screen.

When the switch is pressed on, current flows in the electromagnet. It then attracts the iron rod towards itself, causing the hammer to strike the gong. At the same time, the armature loses contact with the screw and the current is switched off. This causes the electromagnet to lose its magnetism and the armature springs back to its original position to close the circuit once again. Current flows again and the cycle repeats itself till the current is switched off.

Question 2.
What is the chemical effect of electric current? Explain the process of electroplating.
Answer:
Chemical effect of Electric Current: 
When electric current flows through any good conductor solution then it creates an effect in that solution; for example.Take out two carbon rods from unused cells. Clean their caps with sand paper and wind copper wire on them and connect with battery. These two rods are called electrodes, plate connected with positive (+ve) terminal is called anode and (-ve) terminal with which plate is attached is called cathode. The two lines, bigger represents (+ve) terminal and smaller (-ve) terminal. Dip these two terminals either in lemon juice or sodium chloride solution in a plastic container or in a glass. Take precaution-that caps of both the terminals should be out of solution, wait for 3-4 minutes and observe the electrodes. We see that bubbles come out and plates are coated with ions. It happens due to chemical reactions took place due to flow of electricity in the solution, colour of solution can be changed, but these reactions depend upon metal of electrodes and solutions. These are called chemical effect of electric current on chemicals.

Effects of Electric Current Additional Questions Solved

I. Multiple Choice Questions

Question 1.
Who discovered magnetic effect of current?
(a) H C Oersted
(b) Ohm
(c) Flemmimg
(d) Michael Faraday

Question 2.
Current is the flow of:
(a) Protons
(b) Electrons
(c) Charge
(d) Matter

Question 3.
The compound 75 decomposed into its constituents under the effect of electric current is called:
(a) Electrolysis
(b) Hydrolysis
(c) Electroplating
(d) Corrosion

Question 4.
When the ends of metal wire are not connected to a battery:
(a) electrons move from positive electrode to negative electrode
(b) electrons move from negative electrode to positive electrode
(c) electrons move in random directions
(d) protons move in random directions.

Question 5.
The coil of wire contained in heater is known as:
(a) circuit
(b) element
(c) component
(d) Spring

Question 6.
Which of these is not a circuit element:
(a) voltmeter
(b) battery
(c) resistor
(d) potential difference

Question 7.
A cell converts:
(a) electrical energy into chemical
(b) chemical energy into electrical energy
(c) magnetic energy into electrical energy
(d) electrical energy into mechanical energy

Question 8.
The most common industrial application of chemical effects of electric current is:
(a) electroplating
(b) electrolysis
(c) anodising
(d) galvanising

Question 9.
An electrolyte:
(a) has positive charge
(b) has negative charge
(c) show table to home positive and negative charge
(d) should able to conduct charge

Question 10.
An electrolyte is
(a) A solution
(b) A metal plate
(c) A non metal
(d) A liquid that conduct electricity

Question 11.
What is used to protect the circuit
from overload and short circuit?
(a) Fuse
(b) Electric bell
(c) Electric coil
(d) Magnetic needle

Question 12 .
What is the other name of electrolyte cell:
(a) Meter
(b) Electrode
(c) Fuse
(d) Voltmeter

Question 13.
When electricity is passed through water-
(a) hydrogen is evolved at anode
(b) oxygen gas is evolved at cathode
(c) hydrogen is evolved at cathode
(d) no change occurs

Question 14.
Which does not conduct electricity?
(a) Lemon juice
(b) Distilled water
(c) Copper sulphate solution
(d) Sodium chloride ‘

Question 15.
Using LED has an advantage over using a bulb as-
(a) LED makes a non-conducting material a conductor
(b) LED glows faintly
(c) LED glows even with a faint current
(d) Led glows only with a large current

Answers:

1. (a)
2. (c)
3. (a)
4. (c)
5. (b)
6. (d)
7. (b)
8. (d)
9. (c)
10. (d)
11. (a)
12. (d)
13. (c)
14. (b)
15. (c)

Effects of Electric Current Very Short Answer Type Questions

Question 1.
What is electric circuit?
Answer:
Electric circuit is a continuous conducting path for electric current consisting of a source of current.

Question 2.
What do you know about MCB?
Answer:
MCB (miniature circuit breaker) is a switch that automatically stops the current in a circuit if the current in it exceeds the specified maximum limit.

Question 3.
Write the names of two conductors and insulators.
Answer:
Conductors – Copper, Iron, insulators – Plastic, rubber.

Question 4.
Define electromagnet?
Answer:
Electromagnet is a coil of insulated current carrying wire wound around a piece of a magnetic substance.

Question 5.
What is electrolysis?
Answer:
The decomposition of an electrolyte when electricity is passed through it is called electrolysis.

Question 6.
Write the use of chemical effect of electric current.
Answer:
Chemical effect of electric current is used in electroplating.

Question 7.
Name the three effects of electric current.
Answer:
The three effects of electric current are:

1. Heating effect
2. Magnetic effect
3. Chemical effect

Question 8.
What effect of current is observed in electroplating.
Answer:
Chemical effect of electric current.

Question 9.
How does electric current flows?
Answer:
Electric current flows from high to low potential through a conductor.

Question 10.
Name the liquids which are electric conductors?
Answer:
Most of liquid which are electric conductors, are acid solutions, base solutions and salts solutions.

Effects of Electric Current Short Answer Type Questions

Question 1.
Name the basic components of electric circuit.
Answer:
Every electric circuit has three basic components:
(a) a source of electric energy such as an electric cell, a battery or a generator.
(b) an output device such as electric bulb, electric device, motor or lamp to draw current.
(c) a connective device is conducting wire or cable.

Question 2.
Why do we use symbols?
Answer:
We use some standard symbols to represent different components of a circuit.
Using symbols in a circuit makes it-

• Easy to understand
• Quick to draw
• Clean and clear in appearance.

Question 3.
What is an electromagnet? Write the name of four appliances in which it is used?
Answer:
An electromagnet is a coil of insulated wire wound around a piece of a magnetic substance, such as soft iron, which acts as a magnet only as long as the current is flowing in the wire. The magnetic material around which the coil is wound is called the core. The core increases the magnetic effect of the solenoid several times. They are used in electric motors, which find wide application in fans, washing machines, air conditioners, refrigerators, etc.

Question 4.
Explain why electric bulb glows on passing current?
Answer:
When the electric current passes through an electric bulb, the filament of the bulb gets heated to a high temperature due to the heating effect of current. So, the bulbs starts to glow. Sometimes the current is too weak and filament of bulb does not get heat sufficiently and bulb does not glow.

Question 5.
What is tester?
Answer:
An electric instrument which is used to check the flow of electric current is called tester. It is attached to the terminals of the electric circuit. If the bulb of tester glows, it confirms that electric current is flowing through the circuit.

Question 6.
The ordinary water can conduct electricity while distilled water does not. Explain why.
Answer:
The water that we get from different sources,
such as taps, hand pumps, wells and ponds is not pure. It may contains several salt dissolved in it. This water is thus good conductor of electricity. Distilled water is free of salt due to which it is a poor conductor.

Effects of Electric Current Long Answer Type Questions

Question 1.
Explain the process of electroplating of copper on carbon rod experimentally.
Answer:
Take copper sulphate solution in a glass trough. Dip a carbon rod in the solution. Use it as the cathode, i.e. connect it to the negative terminal of the battery. Take a pure copper strip, dip it in the solution and use it as anode, i.e. connect it to the positive terminal. Pass electricity through the solution by closing the circuit. The positively charged copper ions from the solution will move towads the carbon rod which is acting as the cathode. The copper ions that are positively charged get attracted towards the negative electrode, the carbon rod get deposited on it. But how does the loss of copper from the solution get compensated? The copper anode releases copper ions into the solution, thus compensating for the loss. Since copper sulphate is an ionic compound, it constitutes ions-

When electricity is passed through the solution, the cations (i.e. positively charged copper ions) move towards the cathode. Here they gain electrons and get deposited as copper metal.
At cathode:
Cu²⁺ + 2e^– → Cu
The sulphate ions remain in the solution. Copper at anode loses electrons and goes into the solution as copper ions to replenish the copper ions deposited at cathode.
An anode:
Cu→ Cu²⁺+ 2e^–

Question 2.
What is short circuit? Explain its causes and harms?
Answer:
When due to any reason phase and neutral joins directly then it is called short circuit. In such case very high voltage passes which causes fire due to high heating effect and could burn. Some times when more than one appliances are attached to single socket. It is called over loading on electric circuit. We should not attach more than one appliances or plugs in one socket.
Causes of Short Circuit:

1. When quantity of current is more than limit of security, wire gets heated and plastic coat melts it allows phase and neutral to join and cause short circuit.
2. When wires become old they break and cause short circuit. Harms from Short Circuit Due to short circuit high voltage current flow which results into fire and can cause severe accidents. To overcome this and save electric appliances in the series of electric circuit such a plug should use which could melt when limit of security cross, it closes the circuit such a wire is called fuse wire. Such a special wire is used today in expensive appliances like T.V., Fridge etc.

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