To determine resistance per cm of a given wire by plotting a graph of potential difference versus current

Our Objective Our objective is to determine the resistance per centimeter of a given wire by plotting a graph of potential difference versus electric current. The Theory According to the Ohm's law, "The electric current flowing through a conductor is directly proportional to the potential difference across its ends provided the physical conditions (temperature, dimensions, pressure) of the conductor remains the same." If I is the current flowing through a conductor and V is the potential difference across its ends, then according to Ohm's Law, where, R is the constant of proportionality. It is known as resistance of the conductor, or R depends upon the material, temperature and dimensions of the conductor. In S.I. units, the potential difference 'V' is measured in volt and the current 'I' in ampere, the resistance 'R' is measured in ohm. To establish the current-voltage relationship, it is to be shown that the ratio V / I remains constant for a given resistance and therefore a graph between the potential difference(V) and the current (I) must be a straight line. The value of unknown resistance can be calculated using the equation , Here R is a constant. To find the length of the resistance wire, l. Then This gives the resistance per unit cm. Learning Outcomes • Students learn Ohm’s law. • Students know the relation between voltage, current and resistance. Copyright @ 2023 Under the NME ICT initiative of MHRD

EXPERIMENT -1 OHM’S LAW AIM: To determine resistance per cm of a given wire by plotting a graph of potential difference versus current. APPARATUS: A voltmeter, an ammeter, unknown resistance, rheostat, key, battery and connecting wires. THEORY AND FORMULA: Ohm’s law states that when a steady current flows through a conductor the ratio of potential difference between the ends of the conductor and current flowing through it is constant, provided that the physical condition of the conductors ,such as length temperature etc. do not change. If V is the potential difference and I is the current then I α V Or V / I = constant(R) R is the resistance of the conductor Resistance of the wire R = Δ V / ΔI (from the graph) If L is the Length of the wire, Resistance per cm of given wire = R/L Ω/cm 0 PROCEDURE 1 Arrange the apparatus according to the circuit diagram as shown. 2 Note the zero correction of ammeter and voltmeter, if any 3 Insert the key K and slide the rheostat contact starting from the left end to the right end. Note down the observations in the ammeter and voltmeter. 4 Go on increasing the current step by step with the help of rheostat and take at least six sets of observations. Tabulate all the observations. 5 Draw the graph by plotting voltmeter reading (V) along the X axis and ammeter reading (I) along the Y axis. SOURCES OF ERROR 1 The connections may be loose 2 The ratio of V/I may not be constant due to heating caused by passage of current for longer interval of ti...

Aim: To determine the resistance per cm of a given wire by plotting a graph of potential difference versus current, and hence to determine its resistivity. The Theory: What does Ohm's Law state? According to the Ohm's law, "The current flowing through a conductor is directly proportional to the potential difference across its ends provided the physical conditions (temperature, dimensions, pressure) of the conductor remains the same." If I be the current flowing through a conductor and V be the potential difference across its ends, then according to Ohm's Law, where, R is the constant of proportionality. It is known as resistance of the conductor. Or ..the working formula R depends upon the material, temperature and dimensions of the conductor. In S.I. units, the potential difference V is measured in volt and the current I in ampere, the resistance R is measured in ohm. How do we establish the current-voltage relationship? To establish the current-voltage relationship, it is to be shown that the ratio V /I remains constant for a given resistance, therefore a graph between the potential difference(V) and the current (I) must be a straight line. How then do we find the unknown values of resistance? It is the constant ratio that gives the unknown values of resistance, For a wire of uniform cross-section, the resistance depends on the length l and the area of cross-section A. It also depends on the temperature of the conductor. At a given temperature the resistance, where ρ is ...

To Determine Resistance per cm of a Given Wire By Plotting a Graph of Potential Difference Versus Current - Physics Practical Class 12 Viva Questions with Answers • Define Ohm’s law. Answer. The current that flows through most conductors is directly proportional to the voltage applied. The voltage across a conductor is directly proportional to the current flowing through it, provided all physical conditions and temperatures remain constant. • What is the formula of Ohm’s law? Answer. Ohm’s law is given by the formula: V=IR Where, I=current, V=volatge, and R=Resistance. • What is specific resistance? Answer. The resistance offered per unit length and unit cross-sectional area when a known amount of voltage is applied is known as the specific resistance. • What is the SI unit of the potential difference? Answer. The SI unit of the potential difference is volt. • The current is measured in which unit? Answer. The unit of electric current is Ampere. • What is the unit of resistance? Answer. The unit of the electrical resistance is Ohms. • Does the resistance depend on the temperature? Answer. Yes, the resistance depends on the temperature. As the temperature increases, the resistance also increases. • What are the various sources of error while performing this experiment? Answer: Various sources of error are: • The instrument screws may be loose. • Lack of thick connecting wires. • Using rheostat of high resistance. • What is electrical conductivity? Answer. It is the measure ...