Practical No. 03: Determination of resistance by Ohm’s law.
XIII. Interpretation of Results
- The straight-line graph of Voltage (V) vs. Current (I) passing through the origin confirms that the wire obeys Ohm’s law.
- The resistance value calculated from the slope of the graph matches the average resistance calculated from the observations, validating the experiment.
XIV. Conclusions and Recommendations
- Ohm’s law (V = IR) is successfully verified for the given wire.
- It is highly recommended to switch on the circuit only while taking readings to prevent heating of the wire, which can change its resistance.
XV. Practical Related Questions & Answers
Q1. State the function of rheostat in this lab experiment.
- Answer: The rheostat acts as a variable resistor. Its main function is to control and vary the amount of electric current flowing through the circuit, allowing us to take multiple pairs of voltage (V) and current (I) readings.
Q2. A potential difference of 15V appears across the ends of a resistor when 5A of current flows through it. Find resistance of the resistor?
- Answer:
- Formula: Resistance (R) = Voltage (V) / Current (I)
- Given Data:
- Voltage (V) = 15 V
- Current (I) = 5 A
- Calculation:
- R = 15 V / 5 A
- R = 3 Ohms (Ω)
Q3. If the voltage across a fixed value of resistance is increased five times, what will be the variation in current? Does the resistance depend on the temperature?
- Answer:
- Variation in Current: From Ohm’s law, Current (I) = Voltage (V) / Resistance (R). If resistance (R) is constant and voltage is increased five times, the current will also increase five times.
- Dependence on Temperature: Yes, the resistance of a conductor depends on temperature. For most metals, resistance increases with an increase in temperature.
Q4. Calculate the voltage if a resistance of 25 Ω produces a current of 250 amperes.
- Answer:
- Formula: Voltage (V) = Current (I) × Resistance (R)
- Given Data:
- Resistance (R) = 25 Ω
- Current (I) = 250 A
- Calculation:
- V = 250 A × 25 Ω
- V = 6250 V
Q5. State Ohm’s Law.
- Answer: Ohm’s Law states that the electric current (I) flowing through a conductor is directly proportional to the potential difference (V) applied across its ends, provided the physical conditions (like temperature) remain constant.
- Mathematical expression: V = IR (where R is the resistance).
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