Lesson 4 Electric Charge and Electric Current
9th Science Guide: Welcome to Lesson 4 of our study on Electric Charge and Electric Current. In this post, we will provide the book back answers to various questions related to Electric Charge and Electric Current. These questions cover topics such as electric charge, electric current, resistance, potential difference, and more. By going through these answers, you will enhance your understanding of the concepts discussed in this lesson. So, let’s dive in and explore the correct answers!
Electric Charge and Electric Current Book Back Answers
Here, you will find answers for various sections related to the lesson on Electric Charge and Electric Current, including “Choose the Correct Answer,” “Fill in the Blanks,” “State Whether True or False,” and more.
I. Choose the Correct Answer
1. In current electricity, a positive charge refers to,
- presence of electron
- presence of proton
- absence of electron
- absence of proton
Ans: absence of electron
2. Rubbing of comb with hair
- creates electric charge
- transfers electric charge
- either (a) or (b)
- neither (a) nor (b)
Ans: transfers electric charge
3. Electric field lines from positive charge and in negative charge.
- start; start
- start; end
- start: end
- end; end
Ans: start: end
4. Potential near a charge is the measure of its _______ to bring a positive charge at that point.
5. Heating effect of current is called,
- Joule heating
- Coulomb heating
- voltage heating
- Ampere heating
Ans: Joule heating
6. In an electrolyte the current is due to the flow of,
- positive ions
- both (a) and (b)
- neither (a) nor (b)
Ans: both (a) and (b)
7. Electroplating is an example for
- heating effect
- chemical effect
- flowing effect
- magnetic effect
Ans: chemical effect
8. Resistance of a wire depends on,
- nature of material
- all the above
Ans: all the above
9. The following is not a safety device.
- trip switch
- ground connection
10. In India the frequency of alternating current is,
- 220 Hz
- 50 Hz
- 5 Hz
- 100 Hz
Ans: 50 Hz
II. Match the Following
|1. Electric Charge||ohm|
|2. Potential difference||ampere|
|3. Electric field||coulomb|
|4. Resistance||newton per coulomb|
|5. Electric current||volt|
|Ans : 1 – C, 2 – E, 3 – D, 4 – A, 5 – B|
III. True or False
1. Electrically neutral means it is either zero or equal to positive and negative charges.
2. Ammeter is connected in parallel to any electric circuit.
3. The anode in the electrolyte is negative.
4. Current can produce a magnetic field.
5. Electric fuse works on the Joule heating principle
IV. Fill in the Blanks
1. Electrons move from _________ potential to _________ potential.
Ans: high, low
2. The direction opposite to the movement of the electron is called _________ current.
3. The e.m.f of a cell is analogues to ___________________ of a pipe line.
4. The domestic electricity in India is an ac with a frequency of _________ Hz.
5. Trip switch is a _________ safety device.
Ans: electro mechanical
V. Conceptual Questions
1. A bird sitting on a high power electric line is still safe. How?
- Electricity flows along the path of least (low) resistance. Birds have high resistance.
- Birds are not good conductors of electricity. Their cell and tissue don’t offer electrons an easier route.
As a result the electricity by passes the bird.
2. Two resistors 12Ω and 6Ω are first connected in series and then in parallel. The current-voltage graph for the two connections will be represented by which lines in the graph?
Resistance in the parallel circuit is less than the resistance in the series. The slope of line B is less than the slope of line A. Hence the resistance of line B is less than the resistance of line A. Thus line B represents a parallel circuit and line A represents a series circuit.
3. Can electroplating be possible with alternating current?
Resistance in the parallel circuit is less than the resistance in series. The slope of line B is less than the slope of line A. Hence the resistance of line B is less than the resistance of line A. Thus the line B represent parallel circuit and the line A represent series circuit.
4. Does a solar cell always maintain the potential across its terminals constant? Discuss.
The potencial across the terminals of the solar cell changes according to the intensity of the sun. It gives high potencial at high temperature and low potencial at low temperature.
5. What is the efective resistance across the terminals a and b of the arrangement of resistors?
|Resistance in series combination||= Rs = R1+R2 = 2R|
|Resistance in parallel combination 1/Rp||= 1/R1 +1/R2|
|= 1/R +1/R+ 1/2R|
|R||=2/5 R Ω|
VI. Answer the Following
1. On what factors does the electrostatic force between two charges depend?
- Value of charges on them,
- Distance between them
- Nature of medium between them.
2. What are electric lines of force?
The electric lines of force are straight or curved paths along which a unit positive charge tends to move in the electric field.
3. Define electric field.
An electric field at a point is a measure of force acting on a unit positive charge placed at that point.
4. Define electric current and give its unit.
Current is the rate at which charges flow past a point on a circuit. The standard SI unit for current is ampere with the symbol A.
5. State Ohm’s law.
Ohm’s law states that electric potential difference across two points in an electrical.circuit is directly proportional tothe current passing through it Ohm’s law is written as,
V = I R
6. Name any two appliances which work under the principle of heating effect of current.
Iron box, Water Heater , toster
7. How are the home appliances connected in general, in series or parallel. Give reasons.
In a household electric circuit, different home appliances are connected in parallel to
one another due to the following reasons:
- The appliances can be operated independently. If one appliance is switched off, others remain unaffected.
- Each appliance gets the same constant voltage.
- In parallel connection of electrical appliances, the overall resistance of the circuit it reduced due to which the current form the power supply is high.
8. List the safety features while handling with electricity.
The metal bodies of all the electrical appliances are to be connected to the ground by means of a third wire apart from the two wires used for electrical connection.
It is an electromechanical device which does not allow a current beyond a particular value by automatically switching off the connection. We have trip switches of various current ratings used for specific purposes. It works on relay principle.
A fuse is another safety mechanism which works on joule heating principle. Fuse is a wire made up of a Nickel and Chromium alloy which has a definite melting point. If current passes through the fuse beyond a particular desired value, the excess heat produced melts the fuse wire, thus the electrical connection is cut-off.
9. On what factor does the resistance of a wire depend at a particular temperature?
The resistance offered by a material at a particular temperature depends on the,
- geometry of the material and
- nature of the material
8. Draw a circuit with a 2Ω and 5Ω resistors in series. Connect another 3Ω resistor parallel to the above connection.
1. Rubbing a comb on hair makes the comb get – 0.4C.
(a) Find which material has lost electron and which one gained it.
Comb gained electrons. Dry hair lost electron.
(b) Find how many electrons are transferred in this process.
No. of electrons transferred = – 0.4 C
|1 coulomb =||6.25 × 1018 electron|
|– 0.4 C =||0.4 × 6.25 × 1018 electrons|
|= – 2.5 × 1018 electrons|
2. Calculate the amount of charge that would flow in 2 hours through an element of an electric bulb drawing a current of 2.5A.
|Current I =||2.5 A|
|time t = 2 hours =||2 × 3600 seconds|
|t =||7200 s|
|Amount of charge Q =||I × t|
|Q =||18,000 C|
3. The values of current (I) flowing through a resistor for various potential differences V across the resistor are given below. What is the value of the resistor?
Resistance of the resistor R = V2-V1/I2-I1
= 13.2-10.2/ 4-3
= 3/1= 3Ω
R = 3Ω
By finishing this post and reading through the provided answers for Electric Charge and Electric Current, you have strengthened your understanding of how electric charge and electric current work. Make sure to carefully go over the explanations and solutions to improve your knowledge of this topic. Keep an eye out for more lessons and exercises that will help you deepen your understanding of physics.
Last Updated: 30th June 2023