Question

Ohm Law and Resistivity

 

1. According to Ohm's Law, for a constant R resistance Does the current in a circuit increase or decrease if we increase the voltage? Explain your answer based on the corresponding formula.

2. According to Ohm's Law, for a constant voltage, does the value of the current increase or decrease if we decrease the resistance with a rheostat connected in series in the circuit? Explain with your words based on the corresponding formula.

3. Calculate the current that passes through a circuit if a voltage of 110 volts is applied and it has a resistance of 30 ohm.

4. Calculate the resistance that a circuit has if, when applying a voltage of 50 volts, the measured current intensity is 0.02 Amperes.

5. Calculate the voltage applied to a 100 ohm resistance circuit if the measured current is 0.02 Amps.

6. Explain how we must connect an ammeter in the circuit to measure the intensity of current flowing through one of the resistors of the circuit.

7. Explain how we should connect a voltmeter in the circuit to measure the voltage at a resistor.

8. Name four factors on which the resistance value of a metal conductor depends.

9. Why is resistivity called an intrinsic property?

10. Pose the resistivity formula and clear the resistance, length and cross-sectional area.

Answer 1

Answer 1.

According to Ohm's Law V = I R where V is the potential difference across conductor of Resistance R, I is the current flowing in that conductor due to application of V

I question Given that R is constant and we increase the voltage therefore current I in the circuit will increase because Applied voltage is proportional to Current according to the formula of Ohm's law.

Answer 2.

If we decrease the resistance with the help of rhehostat connceted in series then value of current will increase because V = I R says that if V is constant then product of I and R constant so if one of them is decreased then other will increase.

Answer 3.

Given V = 110 V and R = 30 Ohm

Current I = V/ R = 110 / 30 = 3.66666 Ampere

Answer 4.

given V = 50 Volt and I = 0.02 Ampere

R = V / I = 50 / 0.02 = 2500 Ohm = 2.5 kilo Ohm

Answer 5

Given R = 100 Ohm and current I = 0.02 Ampere

V = I R = 0.02 x 100 = 2 Volt

Answer 6.

We must connect Ammeter in the series with the resistnace to measure the intensity of current because when it is connected in series it will measure the total current flowing throught that Resistance.

Answer 7.

We should connect the voltmeter in parallel with the Resistance across which we have to measure the potential difference because V is equal in parallel circuit.

Answer 8.

Resistance of a metal conductor depend upon

(a) Length of the conductor . It is proportional to the length of the conductor

(b) Area of cross section . The resistance is inversely proportional to the area of cross section of the conductor wire.

(c) Temperature. As the temperature of surroundings increse the value of resistance of conductor also increase Hence R is directly proportional to the temperature.

(d) number of free electrons in the conductor. The resistance of the conductor is inversely proportional to the number of eleectrons in the conductor.

Answer 9.

Resistivity is called intrinsic property because it does not depend on the size of the conductor like length or area etc but it is the property of the material.

Answer 10.

resistivity (ρ) = R A / L

where R is the resistance of the conductor

A is the area of cross section of the conductor

L is the length of the conductor.