Dependence of Resistance on Temperature

Q.

The temperature coefficient of resistance for a wire is 0.00125${/}^{\circ }C$. At 300K its resistance is 1 ohm. The temperature at which the resistance becomes 2 ohm is

1. 1154 K
2. 1100 K
3. 1400 K
4. 1127 K

Q. A resistance wire connected in the left gap of a meter bridge balances a $10\Omega$ resistance in the right gap at a point which divides the bridge wire in the ratio $3:2$. If the length of the resistance wire is $1.5\text{m}$, then the length of $1\Omega$ of the resistance wire is:

1. $1.0\times {10}^{-2}\text{m}$
2. $1.5\times {10}^{-2}\text{m}$
3. $1.5\times {10}^{-1}\text{m}$
4. $1.0\times {10}^{-1}\text{m}$

Q.

Why does the resistance of a conductor increase with an increase in temperature?

Q. The resistance of a conductor is $5\text{ohm}$ at ${50}^{\circ }\text{C}$ and $6\text{ohm}$ at ${100}^{\circ }\text{C}$. Its resistance at $0^{\circ }\text{C}$ is

1. $3\text{ohm}$
2. $4\text{ohm}$
3. $1\text{ohm}$
4. $2\text{ohm}$

Q. 41.The resistance of a tungsten filament @ 150*C is 133 Ohms. Find resistance @ 500*C. The temperatue co-efficient of resistance of tungsten is 0.0045per*C.

Q.

What is the unit of specific conductance in Ohm

Q. In a zener regulated power supply a zener diode with Vz=6V is used for regulation. The load current is to be 4mA and the unregulated input is 10V. What should be the value of series resistor R?

Q. A potentiometer wire of length L and a resistancer are connected in series with a battery of e.m.f.E and a resistance r, . An unknown e.m.f. E isbalanced at a length of the potentiometer wire.The e.m.f. E will be given by7.\lbrack Re-AIPMT-2015\rbrack

Q.

Factors on which the specific resistance of a wire depends

Q.

Why does breakdown occur in reverse bias ?

Q. How is the drift velocity in a conductor affected with the rise in temperature?

Q. 14. The value of current through 2 ohm resistor is

Q.

The resistance of a wire at ${20}^{\circ }C$ is $20\Omega$ and at ${500}^{\circ }C$ is $60\Omega$. At which temperature resistance will be $25\Omega$?

1. ${70}^{\circ }C$
2. ${50}^{\circ }C$
3. ${80}^{\circ }C$
4. ${60}^{\circ }C$

Q.

The resistances of an iron wire and a copper wire at 20 ${}^{\circ }$ are 3.9 $\Omega$ and 4.1 $\Omega$ respectively. At what temperature will the resistances be equal ? Temperature coefficient of resistivity for iron is 5.0 ${\times }^{-3}{K}^{-1}$ and for copper it is 4.0 $\times {10}^{-3}{K}^{-1}$. Neglect any thermal expansion.

Q. (i) Draw a labelled diagram of a step-down transformer. State the principle of its working.
(ii) Express the turns ratio in terms of voltages.
(iii) Find the ratio of primary and secondary currents in terms of turns ratio in an ideal transformer.
(iv) How much current is drawn by the primary of a transformer connected to 220 V supply when it delivers power to a 110 V - 550W refrigerator ?

Q.

Which does metal resistance decrease with an increase in temperature?

Q.

Resistivity does not change if

1. Material is changed.

2. Temperature is changed.

3. The shape of the resistor is changed.

4. Both material and temperature are changed.

Q.

Why does a superconductor have zero resistance ?

Q. A heating element using nichrome connected to a 230 V supplydraws an initial current of 3.2 A which settles after a few seconds to a steady value of 2.8 A. What is the steady temperature of the heatingelement if the room temperature is 27.0 °C? Temperature coefficientof resistance of nichrome averaged over the temperature rangeinvolved is 1.70 × 10–4 °C–1.

Q. Using Bohr model, calculate the electric current created by the electron when the $H-atom$ is in the ground state.

Q.

What happens to the resistance as the conductor is made thinner?

Q. A $200\Omega$ resistor has a certain color code. If one replaces the red color by green in the code, the new resistance will be

1. $100\Omega$
2. $400\Omega$
3. $500\Omega$
4. $300\Omega$

Q. The operating temperature of the filament of lamp is $2000{}^{\circ }C$. The temperature coefficient of the material of filament is $0.005{}^{\circ }{C}^{-1}$. If the atmospheric temperature is $0{}^{\circ }C$, then the current in the $100W-200V$ lamp when it is switched on is nearest to

1. $2.5A$
2. $3.5A$
3. $4.5A$
4. $5.5A$

Q.
What will be the equivalent resistance between the terminals A and B of the infinite resistive network shown in figure ?

1. $\frac{(\sqrt{3}+1)}{2}$
2. $\frac{(\sqrt{3}-R)}{2}$
3. $3\frac{R}{2}$
4. $(\sqrt{3}+1)R$

Q.

Why do semiconductors conducts electricity at high temperatures?

Q.

Temperature coefficient of resistance of platinum is $4\times {10}^{-3}{K}^{-1}$ at $0^{\circ }$C. The temperature at which the increase in the resistance of platinum wire is 10% of its value at $0^{\circ }$C.

1. ${250}^{\circ }C$
2. ${500}^{\circ }C$
3. ${25}^{\circ }C$
4. ${50}^{\circ }C$

Q. A potentiometer wire is 100 cm long and a constant potential difference is maintained across it. Two cells are connected in series first to support one another and then in opposite direction. The balance points are obtained at 50cm and 10cm from the positive end of the wire in the two cases. The ratio of emf's is:

1. 5 : 1
2. 5 : 4
3. 3 : 4
4. 3 : 2

Q. Resistance in the two gaps of a metre bridge are $15\Omega$ and $45\Omega$ respectively. If the resistances are interchanged, the balance point shifts by

1. $50\text{cm}$
2. $25\text{cm}$
3. $40\text{cm}$
4. $20\text{cm}$

Q. In the method using the transformers, assume that the ratio of the number of turns in the primary to that in the secondary in the step-up transformer is $1:10.$ If the power to the consumers has to be supplied at $200V,$ the ratio of the number of turns in the primary to that in the secondary in the step-down transformer is

1. $200:1$
2. $50:1$
3. $150:1$
4. $100:1$

Q.

The input characteristics of a transistor in CE mode is the graph obtained by plotting

1. $I_B$ against IC at constant $V_{CE}$

2. $I_B$ against $V_{BE}$ at constant $V_{CE}$

3. $I_B$ against IC at constant $V_{BE}$

4. $I_B$ against $V_{CE}$ at constant $V_{BE}$