Factors That Influence Resistance

Q.

A metallic wire of resistance R is melted and recast to half of its original length while maintaining the original volume. What will the new resistance of the wire be?

1. $\frac{R}{4}$
   

2. $\frac{R}{2}$
   

3. $4R$
   

4. $2R$

Q.

How does the resistance of a wire vary with its area of cross-section?

Q.

The resistance of a conductor increases with increase in temperature.

1. True

2. False

Q.

Thicker wire will have more resistance than a thinner wire. TRUE/FALSE?

1. True

2. False

Q.

Define the resistivity of a conductor.

Q.

The resistance of the filament of a bulb ___ when it glows.

1. increases

2. decreases

3. remains unchanged

4. first increases and then decreases

Q.

Two copper wires, one of length $1\mathrm{m}$ and the other of length $9\mathrm{m}$, are found to have the same resistance. Their diameters are in the ratio?

Q.

1 kg piece of copper is drawn into a wire of 1 mm thickness, and another 1 kg copper piece into a wire of 2 mm thickness. What is the ratio of the resistance of these two wires respectively?

1. 2:1

2. 4:1

3. 8:1

4. 16:1

Q.

The resistance of a material depends upon its material.

1. False

2. True

Q. The amount of heat that is produced in a conductor due to current flow is dependant on the strength of the current.

1. True
2. False

Q.

A given piece of wire of length L radius r and resistance R is stretched uniformly to a wire of radius $\frac{r}{2}$. The new resistance is:

1. 4 R

2. 16 R

3. $\frac{R}{4}$

4. $\frac{R}{16}$

Q.

A wire 1 m long has a resistances of 1Ω. If it is uniformly stretched so that its length increases by 25%, then what is its increase in resistance?

1. 25%

2. 77.33%

3. 56.25%

4. 50%

Q.

When a potential difference of 2 V is applied across the ends of a wire of $5m$ length, a current of $1A$ flows through it. Calculate the resistance across the ends of the wire if its length is doubled.

1. 3 ohm

2. 4 ohm

3. 5 ohm

4. 2 ohm

Q.

What length of a copper wire of cross-sectional are 0.01 mm², resistivity 1.7 × 10^–8 Ohm m, will be needed to prepare a resistance of 1.7 kΩ?

1. 0.1 km

2. 0.7 km

3. 1 km

4. 10 km

Q.

The resistance of a metal wire of length 1m is 26 ohm. If diameter of wire is 0.3mm what will be the resistivity of the metal at that temperature.

1. 1.62 x ohm m

2. 6.02 x ohm m

3. 1.53 x ohm m

4. 1.82 x ohm m

Q.

A wire has a diameter of 0.5 mm and a resistivity of 1.6 × ${10}^{-6}$ ohm cm. How much of this wire would be required to make a 10 ohm coil?

1. 1000 m

2. 112.7 m

3. 157.6 m

4. 57 m

Q.

This section contains 1 Assertion-Reason type question, which has 4 choices (a), (b), (c) and (d) out of which ONLY ONE is correct.

इस खण्ड में 1 कथन-कारण प्रकार का प्रश्न है, जिसमें 4 विकल्प (a), (b), (c) तथा (d) दिये गये हैं, जिनमें से केवल एक सही है।

A : The drift velocity of electrons in a conducting wire will increase, if the temperature of the wire is decreased keeping potential difference constant across the wire.

A : यदि तार के सिरों पर विभवान्तर को नियत रखते हुए तार के ताप में कमी की जाती है, तब चालक तार में इलेक्ट्रॉनों का अपवाह वेग बढ़ेगा।

R : On decreasing the temperature, the relaxation time increases.

R : ताप में कमी करने पर, विश्रांति काल बढ़ता है।

1. Both (A) and (R) are true and (R) is the correct explanation of (A)
   
   (A) तथा (R) दोनों सही हैं तथा (R), (A) का सही स्पष्टीकरण है
2. Both (A) and (R) are true but (R) is not the correct explanation of (A)
   
   (A) तथा (R) दोनों सही हैं लेकिन (R), (A) का सही स्पष्टीकरण नहीं है
3. (A) is true but (R) is false
   
   (A) सही है लेकिन (R) गलत है
4. (A) is false but (R) is true
   
   (A) गलत है लेकिन (R) सही है

Q.

A piece of wire of resistance R is cut into five equal parts. These parts are then connected in parallel. If the equivalent resistance of this combination is $R^{{}^{\prime }}$, then the ratio $\frac{R}{R^{{}^{\prime }}}$ is :

1. 25

2. 1/5

3. 5

4. 1/25
   

Q.

The resistance of 100 m long copper wire with diameter 1 mm is = ___ ohms.

Q.

Thicker wire will have more resistance than a thinner wire.

1. True

2. False

Q. The speed of flow of electrons is as low as $1mm/s$ in a circuit. If the length of the wire from the battery to the bulb is $60mm$, what is the time taken for the bulb to light up?

1. Instantaneous
2. $20s$
3. It never lights up
4. $60s$

Q.

Masses of the three wires of same material are in the ratio of 1 : 2 : 3 and their lengths in the ratio of 3 : 2 : 1. Electrical resistance of these wires will be in the ratio of:

1. 1:1:1

2. 1 : 2 : 3

3. 27 : 6 : 1

4. 9:4:1

Q.

How does the resistance of a wire vary with its cross-section area?

Q.

If a metallic wire of resistance R is melted and recast to half of its length, the new resistance of the wire will be?

1. $\frac{R}{4}$
   
2. $\frac{R}{2}$
   
3. R
   
4. 2R

Q.

Certain wire has resistance of 10 Ohm. If it is stretched by 1/10th of its length, then its resistance is nearly:

1. 9 Ω

2. 10 Ω

3. 11 Ω

4. 12 Ω

Q. Which among the following equation gives the correct relation between resistance $\left(R\right)$, length of conductor $\left(L\right)$, area of the cross-section of the conductor $\left(A\right)$ and resistivity$\left(\rho \right)$?

1. $R=\frac{L}{A\times \rho }$

2. $R=\frac{A\times \rho }{L}$

3. $R=\frac{A\times L}{\rho }$

4. $R=\frac{\rho \times L}{A}$

Q.

You have a metal wire of length 1000 m, radius of 0.7 mm andresistivity of the metal is given as $153.86\times {10}^{-6}\Omega m$. Find the resistance of the wire.

1. $40k\Omega$
2. $18k\Omega$
3. $250k\Omega$
4. $100k\Omega$

Q. We know that H=V/R but why a wire having more resistance produces more heat ? Like a nicrome wire

Q.

A resistor of 20 cm length and resistance 5 ohm is stretched to a uniform wire of 40 cm length. The resistance now is-

1. 10 Ω

2. 5 Ω

3. 20 Ω

4. 200 Ω

Q.

Why does the filament of the bulb is spiral in shape?