Advertisements
Advertisements
प्रश्न
Answer the following question.
Distinguish between Ohmic and non-ohmic substances; explain with the help of example.
Advertisements
उत्तर
| Ohmic substances | Non-ohmic substances |
| 1. Substances which obey ohm’s law are called ohmic substances | 1. Substances which do not obey ohm’s law are called non-ohmic substances. |
| 2. Potential difference (V) versus current (I) curve is a straight line. | 2. Potential difference (V) versus current (I) curve is not a straight line. |
| 3. Resistance of these substances is constant i.e. they follow linear I-V characteristic. | 3. Resistance of these substances is a function of V or I. |
| 4. Expression for resistance is, R = `"V"/"I"` | 4. Expression for resistance is, R = `lim_(Δ"l"→0)(Δ"V")/(Δ"I")="dV"/"dI"` |
| 5. Examples: Gold, silver, copper etc. | 5. Examples: Liquid electrolytes, vacuum tubes, junction diodes, thermistors etc. |
APPEARS IN
संबंधित प्रश्न
When a 12 V battery is connected across an unknown resistor, there is a current of 2.5 mA in the circuit. Find the value of the resistance of the resistor.
Name the law which is illustrated by the above V−I graph.
The resistors R1, R2, R3 and R4 in the figure given below are all equal in value.
What would you expect the voltmeter A, B and C to read assuming that the connecting wires in the circuit have negligible resistance?
What is the necessary condition for a conductor to obey Ohm’s law?
What is an ohmic resistor? Give one example of an ohmic resistor. Draw a graph to show its current voltage relationship. How is the resistance of the resistor determined from this graph?
In a conductor 6.25 × `10^16` electrons flow from its end A to B in 2 s. Find the current flowing through the conductor (e = 1.6 × `10^-19` C)
A wire of resistance 9 ohm having length 30 cm is tripled on itself. What is its new resistance?
Show by a diagram how two resistors R1 and R2 are joined in parallel. Obtain an expression for the total resistance of the combination.
Consider the sacle of voltmeter shown in the diagram and answer the following questions :
(a) What is the least count of the voltmeter?
(b) What is the reading shown by the voltmeter ?
(c) If the voltmeter is connected across a resistor of 20 `Omega` how much current is flowing through the resistor?
Fig. represents the circuit used for the verification of ohm's law. Label the different parts from A and F. State the function of each.
Define the following:
Coulomb
The ratio of the potential difference to the current is known as ________.
State macroscopic form of Ohm’s law.
What is ohmic device?
Obtain the macroscopic form of Ohm’s law from its microscopic form and discuss its limitation.
Two cells each of 5V are connected in series across an 8Ω resistor and three parallel resistors of 4Ω, 6Ω, and 12Ω. Draw a circuit diagram for the above arrangement. Calculate
- the current drawn from the cell
- current through each resistor
The temperature of a conductor is increased. The graph best showing the variation of its resistance is:
Assertion: The statement of Ohm’s law is K = IR.
Reason: V = IR is the equation which defines resistance.
Calculate the total resistance of the circuit and find the total current in the circuit.
Ohm's law deals with the relationship between ______
Consider a current carrying wire (current I) in the shape of a circle. Note that as the current progresses along the wire, the direction of j (current density) changes in an exact manner, while the current I remain unaffected. The agent that is essentially responsible for is ______.
Two cells of same emf E but internal resistance r1 and r2 are connected in series to an external resistor R (Figure). What should be the value of R so that the potential difference across the terminals of the first cell becomes zero.
What is the resistance of a conductor through which a current of 0.5 A flows when a potential difference of 2V is applied across its ends?
The resistance of a resistor is reduced to half of its initial value. If other parameters of the electrical circuit remain unaltered, the amount of heat produced in the resistor will become ______.
Vinita and Ahmed demonstrated a circuit that operates the two headlights and the two sidelights of a car, in their school exhibition. Based on their demonstrated circuit, answer the following questions.
- State what happens when switch A is connected to:
a) Position 2
b) Position 3 - Find the potential difference across each lamp when lit.
- Calculate the current.
a) in each 12 Ω lamp when lit.
b) In each 4 Ω lamp when lit.
OR - Show, with calculations, which type of lamp, 4.0 Ω or 12 Ω, has the higher power.
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.
