Kerala Syllabus Class 9 Physics - Chapter 7 Electric Current - Questions and Answers
Questions and Answers for Class 9 Physics ധാരാവൈദ്യുതി | Text Books Solution Physics (English Medium) Physics: Chapter 07 Electric Current - Questions and Answers | SAMAGRA Question Bank
ഒമ്പതാം ക്ലാസ്സ് ഫിസിക്സിലെ Electric Current എന്ന പാഠം ആസ്പദമാക്കി samagra തയ്യാറാക്കിയ ചോദ്യോത്തരങ്ങള്.
Class 9 Physics - Electric Current - Question Bank
∎Physics (English Medium Notes)
1. What is the charge acquired by objects due to friction?
Answer: Static electricity
2. What kind of charges do objects acquire due to friction?
Answer: Positive and Negative
3. Due to the transfer of what objects acquire a charge due to friction?
Answer: Electrons
4. What charge is acquired by an object that loses electrons due to friction?
Answer: Positive
5. What charge is acquired by an object that gains electrons due to friction?
Answer: Negative
6. What is the charge of electrons?
Answer: Negative
7. What is the unit of electric charge?
(volt, ampere, coulomb, joule)
Answer: coulomb
8. What is the flow that creates an electric current in a circuit?
Answer: Charge
9. In which direction do gases flow?
Answer: From a region of low pressure to a region of high pressure
10 . The measure of work required to move a unit charge from one point to another in a circuit is the difference in their..........
Answer: Potential difference
11. The energy source used to maintain a potential difference between two points in an electric circuit is called...........
Answer: Source of electricity
12. The potential difference between the terminals of an electric source when there is no electric current from the source to the circuit is the..........
Answer: Electromotive force
13. The potential difference between any two points in a circuit with an electric current is also called..................
Answer: voltage
14. The potential difference is measured using a........
Answer: voltmeter
15. Potential difference =
(Q/W , Q / t , WQ , W/Q)
Answer: W/Q
16. What is the unit of potential difference?
Answer: volt (V)
17. Which letter represents the unit of potential difference?
(A, J, V, s)
Answer: V
18. Find the source of emf from the bracket.
(Rheostat, Resistor, Generator, Switch)
Answer: Generator
19. The positive terminal of the voltmeter should be connected to which terminal of the cell?
Answer: Positive
20. Which of the following is a primary cell? (Mobile phone battery, Dry cell, Laptop cell, Car battery)
Answer: Dry cell
21. How does a static electric charge occur when objects are rubbed?
Answer: Due to the transfer of electrons
22. Define potential difference.
Answer: The potential difference between two points in a circuit is the quantity of work done in moving a unit charge between these two points.
23. The commonly used torch cell is an example of a source of emf.
Write down other sources of emf known to you. Write down the energy change that occurs in each of these.
Answer:
| Source of emf | Energy change |
|---|---|
| Torch Cell (Dry Cell) | Chemical energy into electrical energy |
| Generator | Mechanical energy into electrical energy |
| Button cell | Chemical energy into electrical energy |
| Car battery | Chemical energy into electrical energy |
| Solar cell | Light energy into electrical energy |
| Mobile battery | Chemical energy into electrical energy |
24. If 180 J of work is done to move a 30 C charge between two points in a conductor, what is the potential difference between the two points?
Answer: Potential difference V = W/Q = 180/30 = 6 V
25. Write the energy conversion that takes place in a generator.
Answer: Mechanical energy into electrical energy
26. Measure and tabulate the potential difference across the terminals of the following sources of electricity using a voltmeter.
Answer:
| Sources | Potential difference (V) |
|---|---|
| Torch Cell (Dry Cell) | 1.5 |
| Button cell | 3 |
| Volta cell | 1.1 |
| Mobile battery | 3.6 to 3.8 |
| Car battery | 12 |
27. Arrange two torch cells in three different ways as shown in the figure. Measure the potential difference across each of them using a voltmeter and tabulate them.
Answer:
28. What is the advantage of connecting cells in series? Give an example of where this method is used.
Answer:
• To get a higher voltage
• In a TV remote control, torch, etc
Answer: To get current for a longer time
30. What is the maximum potential difference that can be obtained using four 1.5 V cells?
Answer: 6 V
31. Safety measures to be adopted while using cells/batteries
Answer:
• Do not connect the positive terminal and negative terminal of a battery directly using a conductor (short circuit).
• Do not put cell/battery in the mouth or chew it.
• Do not use the battery if it is overheated.
• Avoid situations where the battery comes in contact with water or fire.
• Metals such as nickel, cadmium and lead in various types of batteries are harmful and should be disposed carefully.
32. Intensity of Electric Current
Answer: Intensity of electric current, or current, is the quantity of electric charge flowing through a conductor per unit time. The letter I is used to denote the intensity of electric current.
33. How is electric current calculated? What is its unit?
Answer: I = Q/t, ampere (A)
34. If 9 C of charge flows through a conductor in 6 seconds, what is the current?
Answer: I =Q/t = 9/6 = 1.5 A
35. Draw a circuit that includes two 1.5 V cells, a switch, an ammeter, and a bulb.
Answer:
Answer: Resistance is the property of a conductor to oppose the flow of current through it.
To measure current
37. Observe the circuit. Tabulate the symbols of the ammeter and voltmeter, their uses and how they are connected in the circuit.
Answer:| Voltmeter | Ammeter |
|---|---|
| -Ⓥ- | -Ⓐ- |
| To measure potential difference | To measure current |
| In parallel to the device | In series with the device. |
| The positive terminal of the voltmeter should be connected to the positive of the cell and the negative terminal to the negative of the cell. | The positive terminal of the ammeter should be connected to the positive of the cell and the negative terminal to the negative of the cell. |
38. State Ohm's law.
Answer: Ohm's law states that the current through a conductor is directly proportional to the potential difference across the conductor when the temperature is constant.
39. Why does a conductor resist electricity?
Answer: When current flows through a conductor, resistance is caused by the collisions between free electrons and atoms in the conductor.
40. What are the factors that influence resistance?
Answer:
• Area of cross-section (thickness) of the conductor
• Length of the conductor
• Temperature of the conductor
• Nature of the material
41. What is the working principle of a rheostat?
Answer: The resistance of a conductor increases with increase in its length
42. Calculate the current in a circuit if 4 Ω and 8 Ω resistors are connected in series with a 3 V battery.
Answer:
R= 4 + 8 = 12 Ω
I = V/R = 3/12 = 0.25 A
Let's Assess
1. Which of the following device converts chemical energy into electric energy?
a) Dry cell
b) Dynamo
c) Solar cell
Answer: a) Dry cell
2. For current to flow from a cell in a closed circuit, the two terminals of the cell must be
a) at high potential.
b) having a potential difference between them
c) at different temperatures
d) at different heights.
Answer: b) having a potential difference between them
3. In which of the following circuits are the ammeter and the voltmeter connected properly?
Answer: (c)
4. Match the terms in column A with those in columns B and C.
Answer:
Answer:
6) In which of the following circuits are bulbs connected in series?
Answer: b, c7. Analyse the circuit given below and answer the following questions.
a) Calculate the effective resistance in the circuit when the switch is turned on.b) What is the current through the circuit?
c) What is the potential difference across the 2 Ω resistor?
d) What is the current flowing through the 1 Ω resistor?
Answer:
a) R = R₁ + R₂ = 1Ω + 2 Ω = 3 Ω
b) I = V/R = 6 v/3 Ω = 2 A
c) V = I x R₂ = 2 A x 2 Ω = 4 V
d) I = 2 A
8. In an electric circuit, in which way are the fan and its regulator connected? parallel / series
Answer: series
9. Consider the following circuits. Which voltmeter shows a reading of 10 V?
Answer: b, d 10. A wire of length 50 cm has a resistance of 5 Ω. If the length is doubled by stretching,
a) what happens to the area of cross-section (thickness) of the conductor?
b) What will be the resistance of the wire?
Answer:
• a) The area of cross-section becomes half.
• b) The new resistance of the wire is 20 Ω.
11. Which of the graphs given below represents Ohm's law?
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