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Question
The voltage - current readings of a certain material are shown in the table given below:
| Voltage (V) | 10 V | 20 V | 30 V |
| Current (I) | 2 A | 3 A | 4 A |
Study the table.
- State whether the conductor used is ohmic or non-ohmic.
- Justify your answer.
- State Ohm's law.
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Solution
a. Here, the ratio of `V/1` for different readings is:
(i) `(10 V)/(2 A) = 5 Ω`
(ii) `(20 V)/(3 A) = 6.66 Ω`
(iii) `(30 V)/(4 A) = 7.5 Ω`
Here, the ratio is not constant, so the conductor is non-ohmic.
b. The ratio of `V/I` remains constant for all values of V and I in an ohmic conductor. Plotting current I against potential difference V results in a straight line that passes through the origin on a graph. Thus, the conductor in question is not ohmic.
c. Ohm's law states that, under constant physical conditions and conductor temperature, the current flowing in a conductor is directly proportional to the potential difference applied across its ends.
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