Superconductors

Q. What are the factors that affect resistivity ? What are superconductors ?

Q.

Is zero resistance possible ?

EXPLAIN .

Q.

What is a superconductor? Give one example of it.

Q.

Give any three characteristics of the material used for making heating appliances.

Q.

A substance has zero resistance below 1K. What is such a substance called?

Q.

Are Superconductors Perfect conductors ?

Q.

What is the temperature of superconductors?

Q.

How is the magnetic field generated in Magnetic Resonance Imaging (MRI)?

1. The magnetic field is generated by superconducting with the help of liquid chlorine.

2. The magnetic field is generated by superconducting coils with the help of liquid helium.

3. The magnetic field is generated by semiconducting coils with the help of liquid helium.

4. The magnetic field is generated by semiconducting coils with the help of liquid chlorine.

Q.

Is ${\mathrm{VO}}_2$ Paramagnetic?

Q. resistance of a metal wire of length 1 meter is 26 ohm at 20 degree celcius . if the diameter of the wire is 3mm, what will be the resistivity of the metal at that temperature ?

Q. Resistance of a metal wire of length 5m is 20Ω at 20⁰. If the diameter of the wire is 0.4mm, what will be the resistivity of the metal at that temperature?

Q. How much will the resistance change if the diameter of the wire is doubled and its length is halved?

Q. Which of the following is/are true about semiconductors?

1. Resistivity decreases with rise in temperature.
2. Resistivity is influenced by the presence of small amount of impurities.
3. Number of free charge carriers per unit volume decrease with rise in temperature.
4. Number of free charge carriers per unit volume, is independent of the temperature.

Q. Superconductor at very low temperature($\approx 0K$) has _____ resistance and at room temperature($\approx 300K$) has _____ resistance

1. $0$, Finite
2. Finite , Finite
3. Finite , $0$
4. $0$ , $0$

Q. Superconductivity is

1. the property of which certain materials show almost zero resistance at 1000 ${}^{0}C$.
2. the property of which certain materials show almost highest resistance at very high temperature
3. the property of which certain materials show almost zero resistance at very low temperature
4. the property of which certain materials show almost zero resistance at very high temperature

Q. Superconductivity is observed at very high temperatures. State true or false.

1. b
2. a

Q. Superconductors are substances which

1. conduct electricity at low temperature
2. offer high resistance to the flow of current
3. offer no resistance to the flow of electricity
4. conduct electricity at high temperatures

Q.

What makes a conductor good?

Q. The resistance of some substances become zero at very low temperature, then these substances are called

1. Good conductors
2. Semi conductors
3. Super conductors
4. Bad conductors

Q. The phenomenon of losing of electrical resistance by a conductor on cooling it to an extremely low temperature is known as

1. superconductivity
2. resistivity
3. conductivity
4. none of above.

Q. Why superconductors at very low temperatures have tremendous applications if used in applications?

1. Due to nearly zero resistance, current decays very fast in superconductor without applying any voltage across it.
2. Due to nearly zero resistance, current persists in superconductor for a long time without applying any voltage across it.
3. Due to nearly zero conductance, current persists in superconductor for a long time without applying any voltage across it.
4. Due to nearly zero resistance, it is practically unaffected by temperature.

Q. A substance has zero resistance below 1 K. What is such a substance called?

1. Superconductor.
2. conductor
3. semiconductor
4. insulator

Q. Conductivity of superconductor is

1. Infinite
2. Very large
3. Very small
4. Zero

Q. Which of the following is NOT true for supeconductors?

1. All known superconductors prior to the ${1980}^{\prime }s$ only worked at temperatures below about $30$ Kelvins (-243$ degrees Celsius)
2. When superconductors are at sufficiently low temperatures, they offer no electrical resistance
3. Liquid helium was used to cool the first super conductors
4. Liquid nitrogen can now be used to cool some kinds of superconductors
5. "High-temperature supercondcutors, " discovered in the ${1980}^{\prime }s$, can operate at room-temperature

Q. The scientific principle involves in production of ultra high magnetic fields is

1. Super conductivity
2. Digital logic
3. Photoelectric effect
4. Laws of thermodynamics.

Q. Match the following materials with their corresponding critical temperature.

1. Lead
2. T < 4.2 K
3. Niobium
4. T < 7.25 K
5. Mercury
6. T < 9.2 K

Q. What is a superconductor?

Q. The conductivity of superconductor is

1. Very less
2. Infinity
3. Zero
4. Very large

Q. Which of the following materials behave as a superconductor at temperature < 10 K.

1. Copper
2. Iron
3. Lead
4. Steel

Q. Give reason -
For electric power transmission, copper or aluminium wire is used.