V–I Relationship (Ohm’s Law Verification) MCQs Quiz | Class 10
This quiz is for Class: X, Subject: Science (Code 086), Unit: Practicals (Unit IV), covering the topic V–I Relationship (Ohm’s Law Verification). It includes questions on measuring voltage and current, determining resistance, and plotting V–I graphs. Attempt all 10 multiple-choice questions and then click ‘Submit Quiz’ to view your results. You can also download a PDF of your answers for revision.
Understanding V–I Relationship and Ohm’s Law
Ohm’s Law, named after German physicist Georg Simon Ohm, describes the fundamental relationship between voltage (V), current (I), and resistance (R) in an electrical circuit. It states that the current flowing through a metallic conductor is directly proportional to the potential difference across its ends, provided its temperature and other physical conditions remain unchanged. This relationship is mathematically expressed as V = IR.
Key Concepts of V-I Relationship and Ohm’s Law:
- Voltage (V): Also known as potential difference, it is the electric potential energy difference per unit charge between two points in a circuit. It is measured in Volts (V) using a Voltmeter, which is always connected in parallel across the component.
- Current (I): This is the rate of flow of electric charge through a conductor. It is measured in Amperes (A) using an Ammeter, which is always connected in series in the circuit.
- Resistance (R): Resistance is the opposition offered by a conductor to the flow of electric current. It is measured in Ohms. For an ohmic resistor, its resistance remains constant at a given temperature, regardless of the voltage across it or the current flowing through it.
Experimental Verification of Ohm’s Law:
To verify Ohm’s Law, an experiment is typically set up with a resistor, an ammeter (in series), a voltmeter (in parallel), a variable power supply (or battery with a rheostat), and a switch.
- Measuring V and I: By varying the voltage using the power supply or rheostat, the corresponding current flowing through the resistor is measured using the ammeter, and the potential difference across the resistor is measured using the voltmeter. Several sets of (V, I) readings are taken.
- Determining Resistance: For each set of readings, the ratio V/I is calculated. For an an ohmic resistor, this ratio should be approximately constant, representing the resistance R.
- Plotting the V-I Graph: The collected data is then plotted on a graph with voltage (V) on the y-axis and current (I) on the x-axis. For a conductor that obeys Ohm’s Law, this graph will be a straight line passing through the origin. The slope of this V-I graph (V/I) gives the value of the resistance (R) of the conductor.
Formula Variations:
| Quantity | Formula | Units |
|---|---|---|
| Voltage (V) | V = IR | Volts (V) |
| Current (I) | I = V/R | Amperes (A) |
| Resistance (R) | R = V/I | Ohms |
Limitations of Ohm’s Law:
Ohm’s Law is not a universal law and has limitations:
- It does not apply to non-ohmic devices like semiconductors, diodes, transistors, etc.
- It does not apply when the temperature of the conductor changes significantly.
- It is not applicable for unilateral circuits (current flows only in one direction).
Quick Revision Points:
- Ohm’s Law: V = IR.
- V-I graph for ohmic devices is a straight line through the origin.
- Slope of V-I graph gives resistance.
- Voltmeter in parallel, Ammeter in series.
- Resistance is measured in Ohms.
- Temperature must be constant for Ohm’s Law to hold true.
Extra Practice Questions:
- What is the purpose of a rheostat in the experimental setup for verifying Ohm’s law?
- If the resistance of a conductor is 10 Ohms and a current of 2 Amperes flows through it, what is the potential difference across its ends?
- Describe two conditions under which Ohm’s Law may not be applicable.
- How would the V-I graph look for a conductor whose resistance increases with increasing temperature?
- Why is it crucial to connect the ammeter in series and the voltmeter in parallel during the Ohm’s Law experiment?
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