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Published on: 07/12/2019
Electric Charge and Electric Current
Download Tamil Nadu 9th Standard Science question papers, model tests, one-mark questions, important questions, and public exam papers in PDF format. Free study materials and answer keys for TN State Board students.
Questions + Answers key
Take MCQ Science Test1.
Rubbing a comb on hair makes the comb get – 0.4C.
(a) Find which material has lost electron and which one gained it.
(b) Find how many electrons are transferred in this process.
2.
Define electric current and give its unit.
3.
Define electric field.
4.
On what factor does the resistance of a wire depend at a particular temperature?
5.
State Ohm’s law.
6.
Does a solar cell always maintain the potential across its terminals constant? Discuss.
7.
Calculate the amount of charge that would flow in 2 hours through an element of an electric bulb drawing a current of 2.5A.
8.
Assertion (A) : A bird perches on a high power line and nothing happens to the bird.
Reason (R) : The level of bird is very high from the ground.
If both assertion and reason are true and reason is the correct explanation of assertion.
If both assertion and reason are true but reason is not the correct explanation of assertion.
If assertion is true but reason is false
If assertion is false but reason is true
9.
Assertion (A) Electric current will not flow between two charged bodies when connected if their charges are same.
Reason (R) Current is the rate of flow of charge.
If both assertion and reason are true and reason is the correct explanation of assertion
If both assertion and reason are true but reason is not the correct explanation of assertion.
If assertion is true but reason is false
If assertion is false but reason is true.
10.
The resistance of a conductor is R. If its length is doubled, then its new resistance will be_______________
R
2R
4R
8R
11.
If in the circuit, power dissipation is 150 W, then R - is___________
2\(\Omega \)
6\(\Omega \)
5\(\Omega \)
4\(\Omega \)
12.
Two resistances R1 and R2 are connected in parallel. Their equivalent resistance is__________
R1+R2
\(\cfrac { { R }_{ 1 }{ R }_{ 2 } }{ { R }_{ 1 }+{ R }_{ 2 } } \)
\(\cfrac { { R }_{ 1 }+{ R }_{ 2 } }{ { R }_{ 1 }{ R }_{ 2 } } \)
\(\sqrt { { R }_{ 1 }+{ R }_{ 2 } } \)
13.
The resistance of a straight conductor is independent of__________
temperature
material
cross-sectional area
shape of cross-section
14.
A current of 2A passing through conductor produces 80 J of heat in 10 seconds. The resistance of the conductor is__________
0.5\(\Omega \)
2\(\Omega \)
4\(\Omega \)
20\(\Omega \)
15.
Write the difference between resistance in series and in parallel.
16.
Calculate the effective resistance between A and B as shown is the figure
1.
a. Comb gained electrons. Dry hair lost electron.
b. No. of electrons transferred = - 0.4 C
1 coulomb 6.25 x 1018 electron
- 0.4 C = 0.4 x 6.25 x 1018 electron
= - 2.5 x 1018 electrons
2.
The electric current is defined as the rate of flow of electric charge through any section of a conductor.
Electric current I = \(\cfrac { Q }{ t } \)
Its unit is Cs-1
Its SI unit: ampere (A).
3.
Electric field is the region around a charged body within which its influence can be experienced (i.e) within which it can attract or repel another charged body.
4.
The resistance offered by a material at a particular temperature depends on the,
(i) geometry of the material and
(ii) nature of the material.
5.
Ohm's law states that electric potential difference across two points in an electrical circuit is directly proportional to the current passing through it that is
V ∝ I
The proportionality constant is the resistance (R) offered between two points. Hence Ohm's law is written as
V = RI (or) V = IR
6.
No, its terminals are not constant because it is the source of direct current. The dc is due to the unidirectional flow of electric charges. In electrical circuits electrons move from lower to higher electrical potential. So battery is used to maintain a potential difference between the two ends.
7.
Time(t) = 2 hours
= 2 x 60 x 60 = 7200 sec
Current flowing (I) = 2.5 A
Amount of charge (Q) = ?
I = Q / t
Q = It
= 2.5A x 7200 sec = 18000 C
8.
(c)
If assertion is true but reason is false
9.
(d)
If assertion is false but reason is true.
10.
(c)
4R
11.
(b)
6\(\Omega \)
12.
(b)
\(\cfrac { { R }_{ 1 }{ R }_{ 2 } }{ { R }_{ 1 }+{ R }_{ 2 } } \)
13.
(d)
shape of cross-section
14.
(b)
2\(\Omega \)
15.
| S.No | Resistance in series | Resistance is parallel |
| 1 | Rs = R1 + R2 + R3 | \(\cfrac { 1 }{ { R }_{ p } } =\cfrac { 1 }{ { R }_{ 1 } } +\cfrac { 1 }{ { R }_{ 2 } } +\cfrac { 1 }{ { R }_{ 3 } } \) |
| 2. | Current remains the same through resistance | Current is inversely proportional to each resistance. Potential difference remains constant |
| 3. | V = V1 + V2 + V3 | I = I1 + I2 + I3 |
| 4. | IR = IR1 + IR2+ + IR3 | \(\cfrac { V }{ R } =\cfrac { 1 }{ { R }_{ 1 } } +\cfrac { 1 }{ { R }_{ 2 } } +\cfrac { 1 }{ { R }_{ 3 } } \) |
| 5. |  |
 |
16.
The equivalent circuit diagram of the given network is as shown is the figure.
\(\cfrac { 1 }{ { R }_{ 1 } } =\cfrac { 1 }{ 2R } +\cfrac { 1 }{ R } \)
\(\cfrac { 1+2 }{ R } =\cfrac { 3 }{ 2R } \)
\({ R }^{ 1 }=\cfrac { 2R }{ 3 } \)
The effective resistance between A and B is
R11 = R + R1 + R
\(R+\cfrac { 2R }{ 3 } +R=\cfrac { 8R }{ 3 } \)
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Tamilnadu Stateboard 9th Standard Subjects
Tamilnadu Stateboard Standards
