The comprehensive approach in Kerala Syllabus 9th Standard Physics Notes Pdf Chapter 7 Electric Current Notes Extra Questions and Answers ensures conceptual clarity.
Kerala Syllabus Std 9 Physics Chapter 7 Electric Current Extra Questions and Answers
Question 1.
A potential difference of 6V is applied across a conductor having 12 Ω resistance. How much current will pass through it? how many times will the current increase if the length of the resistor ¡s halved and a potential difference is doubled?
Answer:
I = \(\frac{V}{R}\) = \(\frac{6}{12}\) = 0.5 A
If length is halved, R = 12 × \(\frac{1}{2}\) = 6
Potential difference V = 2 × 6 = 12 V
I = \(\frac{V}{R}\) = \(\frac{12}{6}\) = 2 A
That is I is increased by 4 times.
Question 2.
Define one volt.
Answer:
If I joule of work is done to move one-coulomb charge from one point to another, then the potential difference between the points is 1 volt.
Question 3.
There should be______ between two points of a conductor, if there is to be a flow of current beÍeen them.
Answer:
Potential difference
Question 4.
If 10 coulomb charge flows in a circuit in 5s, how much is the charge flowing in the circuit ¡n one second?
Answer:
Charge, Q = 10 C
Time, t = 5s
Charge flowing in one second = \(\frac{10}{5}\) = 2 C/s
Question 5.
If one joule of work is done to move one coulomb of charge from one point to another. What will be the potential difference between these points? (2V , 3V, 1V,4V)
Answer:
1V
Question 6.
If 0.2 A current flows through a 100 Ω resistor, what will be the potential difference between the ends of the resistor?
Answer:
I = 0.2 A
R = 100Ω
V = IR = 0.2 × 100 = 20 V
Question 7.
Using the relation in the first word pair, complete the second.
Voltage : Voltmeter
Electric current: ______
Answer:
Ammeter
Question 8.
If 6 cells of 1.5 V each are connected in series
a) What is the total voltage?
b) If they are connected in parallel, what is the total oltage?
c) How can you connect 6 cells to get 3 V?
a) 9V
b) 1.5V
Question 9.
Find the carriers of electric current in each of the following.
a) Copper wire
b) Common salt solution
C) Gases
d) Nichrome wire
Answer:
a) Copper wire- free electrons
b) Common salt solution -ions
c) Gases- ions
d) Nichrome wire- free electron
Question 10.
A battery is a combination of also or more cells. What are the modes in which cells are connected?
Answer:
Series
Question 11.
Write down four salient features of the parallel connection of cells.
Answer:
- If all the cells have equal emf then the emf of the circuits is the same as that of a single cell.
- The total current flowing in the circuit splits up and flows through each cell.
- The internal resistance of the circuit is very low.
- More current can be made available for a longer time under low voltage.
Question 12.
Observe the figure.
a) Name the instrument depicted above.
b) Write the principle based on which this device is designed
c) For what purpose do we use it in a circuit?
Ans:
a) Rheostat
b) The length of a conductor and its resistance are directly proportional to each other.
c) It is used to regulate the current in a circuit by changing the resistance gradually.
Question 13.
The resistance of a 10cm long wire is 12Ω If this is folded into two parts of equal length and included in a circuit, how much will the resistance he produced?
Answer:
When folded into two parts, the length is half and the area of the cross-section is doubled. Due to the decrease in length, resistance is halved. Also, due to the increase in the area of the cross-section, resistance is again halved. So effective resistance
R = 12 × \(\frac{1}{2}\) × \(\frac{1}{2}\) = 3Ω
Question 14.
One of the factors affecting the resistance of a conductor is temperature. Write down the other factors.
Answer:
Length of the conductor. Area of cross-section, Nature of the material.
Question 15.
What is the function of a rheostat?
Answer:
Its function is to regulate the current in a circuit by changing the resistance regularly.