# Samacheer Kalvi 7th Science Term 2 Unit 2 Solutions

## Samacheer Kalvi 7th Science Term 2 Unit 2 Book Back Question and Answers/Solutions:

Samacheer Kalvi Class 7th Std Science Book Back 1 Mark and 2 Mark Question & Answers PDF uploaded and available below. Class 7th Standard New Syllabus 2022 to 2023 Book Back Question & Answer solutions available for both English and Tamil Medium. Class 7 New Science Book Term 2 Unit 2 – Electricity Answers/Solutions Guide are provided on this page. 7th Std Science Book is of 1st Term consists of 7 units, 2nd and 3rd Term consists of 6 units. All Units/Chapters of Term 1st, 2nd, 3rd Science Book Back One, and Two Mark Solutions are given below.

Check Unit wise and  7th New Science Book Back Question and Answers Guide/Solutions PDF format for Free Download. 7th Std English, Tamil, Maths, Science, and Social Science Book Back Questions and Answers available in PDF. Check Science Book Back Solutions below. See below for the Samacheer Kalvi 7th Science Term 2 Chapter 2 Book Back Answers PDF:

### Samacheer Kalvi 7th Science Book Back Chapter 2 Term 2 Answers/Solutions Guide PDF:

7th Science Subject 1 Mark and 2 Mark Solutions Guide PDF available below. Click the Download option to download the book back 1 Mark & 2 Mark questions and answers. Take the printout and use it for exam purposes.

### Electricity

1. In the circuit diagram below, 10 units of electric charge move past point x every second What is the current in the circuit ________. (a) 10 A
(b) 1 A
(c) 10 V
(d) 1 V

2. In the circuit shown, which switches (L, M or N) must be closed to light up the (a) switch L only
(b) switch M only
(c) Switch M and N only
(d) either switch L or switches M and N
Answer: (d) either switch L or switches M and N

3. Small amounts of electrical current are measured in milliampere (mA). How many milliampere are there in 0.25 A ?
(a) 2.5 mA
(b) 25 mA
(c) 250 mA
(d) 2500 mA

4. which of the following circuits are the bulb connected in series? ### II. Fill in the blanks:

1. The direction of conventional current is ____________ to electron flow.
2. One unit of coulomb is charge of approximately ____________ protons or electrons.
3. ____________ is used to measure the electric current.
4. In conducting materials electrons are ____________
5. S.I. unit of Electrical conductivity of a conductor is ____________

1. Opposite
2. 6.242×10
3. Ammeter
4. Loosely
5. siemens/meters

### III. True or false – If false give Hie correct answer:

1. Electron flow is in the same direction to conventional current flow.
Electron flow is in the opposite direction to conventional current flow.

2. The fuse wire does not melts whenever there is overload in the wiring.
The fuse wire melts whenever there is overload in the wiring.

3. In a parallel circuit, the electric components are divided into branches.

4. The representation of the electric current is A.
Answer: False. The representation of the electric current is I.

5. The electrical conductivity of the semiconductor is in between a conductor and an insulator.

### VI. Match the following :

1. Cell – used to open or close a circuit
2. Switch – safety device used in electric circuit
3. Circuit – A complete path for the flow of an electric current
4. Miniature circuit Breaker- Reset by hand, circuit becomes complete once again
5. Fuse – A device which converts chemical energy into electrical energy

1. Cell – A device which converts chemical energy into electrical energy
2. Switch – used to open or close a circuit
3. Circuit – A complete path for the flow of an electric current
4. Miniature circuit Breaker – Reset by hand, circuit becomes complete once again
5. Fuse – safety device used in electric circuit

### V. Analogy:

1. Water : pipe : : Electric current: ______.

2. Copper : conductor : : Wood : ________.

3. Length : meter scale : : Current : ________.

4. milli ampere: micro ampere : : 10 – 3A: _______.

### VI. Assertion and Reason :

1. Assertion (A): Copper1 is used to make electric wires.
Reason (R): Copper has very low electrical resistance.
Option:
A. Both A and R are true and R is the correct explanation of A.
B. Both A and R are true but R is NOT the correct explanation of A.
C. A is true but R is false.
D. A is false but R is true.
E. Both A and R are false .
Answer: A. Both A and R are true and R is the correct explanation of A

2. Assertion (A): Insulators do not allow the flow of current through themselves.
Reason (R): They have no free charge carriers.
A. If both A and R are true and the R is correct explanation of A.
B. If both A and R are true but R is not a correct explanation of A.
C. If A is true and R is false.
D. If both A and R are false.
Answer: A. If both A and R are true and the R is correct explanation of A

### VII. Very short answer :

1. What is the speed of electric current?
Current travels at the speed of 1/100th times the speed of light 0.0002 m/s.

2. What is the S.I unit of electrical conductivity?
The SI unit of electrical conductivity is Siemens / metres (s/m).

3. Name the device used to generate electricity.

4. Define fuse.
Electric fuse is a safety device which is used in household wiring and in many appliances.

5. Name some devices that run using heat effect of electric current
Electric bulb, geyser, Iron box.

6. Name few insulators.
Rubber, wood, plastic, glass.

7. What is a battery?
Batteries are a collection of one or more cells whose chemical reactions create a flow of electrons in a circuit.

1. Define an electric current.
An electric current is measured by the amount of electric charge moving per unit time at any point in the circuit. The conventional symbol for current is I.

2. Differentiate parallel and serial circuits.
Parallel circuits:

1. It is connected by branches.
2. Voltage remains the same across each component of the circuit
3. Each bulb is fully powered.
4. All bulbs stay lit if one goes out.

Serial circuits:

1. It consist of single loop connection.
2. Current remains same in all parts of the circuit.
3. All the bulbs share power.
4. All bulbs go out if one goes out.

3. Define electrical conductivity.