20 Physics -- DC Circuits

A wire is stretched to double it's length. What happens to its resistance and resistivity ?

1 Answers

When a wire is stretched to double its length while maintaining its original cross-sectional area, the resistance of the wire increases, but the resistivity remains unchanged.

The resistance of a wire is directly proportional to its length. By doubling the length of the wire, the resistance also doubles. This relationship is given by the formula R = ρL/A, where R is the resistance, ρ is the resistivity, L is the length, and A is the cross-sectional area.

However, the resistivity of a material is an intrinsic property that depends on the material's composition and temperature. It does not change when the wire is stretched.

What is the smallest number of 1Ω resistors needed such that when arranged in a certain arrangement involving only series and parallel connections, that the equivalent resistance is (7/6)Ω?

A storage battery of emf 8V and internal resistance 0.5ohm is discharged through a parallel combination of to resistor each of resistance 15 ohm. What is the terminal voltage of the battery? [3]a)...

Emf =8V,

Internal resistance r=0.5Ω
R1 = R2 = 15 Ω

Equivalent capacitance of R1 and R2 is

R= 7.5 Ω

now,

emf = I (R+r)
8 = I (7.5+0.5)

8 = I 8
I = 1A

Now,

E= IR+ Ir
E = V + Ir
8 = V + 1x0.5

V= 7.5 volt

a) the value of terminal voltage is less than the emf of battery, since some work needs to be done to overcome the internal resistance of the battery itself.

b)Adding a resistor in series while charging a battery will help to limit the amount of current flowing to a required amount. Also, any damage can be...

A wire is stretched to double its length. what happens to its resistivity???

At constant temperature, resistance(R) of any material is directly proportional to its length(l) and inversely proportional to its cross-section area(A). When any wire is stretched to double its length, the length increases and cross-sectional area decreases as a result of which the resistance(R) becomes 4(R)

you are given n wires each of resistance R. What is the resistance of maximum to minimum resistance that can be obtained from these wires ?

why ammeter is always connected in series?

Since ammeter las low resistance, it is always connected in series with load.

why voltmeter is always connected in parallel with the load resistance?

Since, voltmeter has a high resistance it is always connected in parallel with load.

why do electrons require steady drift velocity?

why do we use connecting wires made up of copper?

Give an example of non-ohmic conductor.

Some of the non-Ohmic conductors are:

Electrolytes
Vacuum tubes
Junction diodes
Transistors, etc

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Connecting resistors in parallel combination with the galvanometer can convert it into ammeter.

If current in an electric bulb drops by one percent, what happens to the power?

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You are given 2 wires each of resistance R . What is the ratio to minimum resistance that can be obtained from these wires .

If we have two wires, each with a resistance of R, the minimum resistance that can be obtained by combining them in a specific way is R/4.

To achieve this minimum resistance, the wires need to be connected in parallel. When two resistors are connected in parallel, the total resistance is given by the formula:

1/R_total = 1/R1 + 1/R2

In this case, substituting R for both R1 and R2, we get:

1/R_total = 1/R + 1/R = 2/R

Taking the reciprocal of both sides:

R_total = R/2

Therefore, the ratio of the...

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Ohm's law states that the current flowing through a conductor is directly proportional to the voltage applied across it, given that the temperature and other physical conditions remain constant. Mathematically, Ohm's law is expressed as:

V = I * R

where V represents the voltage across the conductor, I represents the current flowing through the conductor, and R represents the resistance of the conductor.