নির্দিষ্ট প্রতিরোধের একটি ধাতব তারের `64xx10^(-6) Omega` m এবং দৈর্ঘ্য 1.98 সেমি

A metal wire of specific resistance 64xx10^(-6) Omega m and length 1.98 cm has a resistance of 7 Omega . Find its radius.

Specific resistance of copper, silver and constantan are (1.78 xx 10^(-6) Omega cm, 10^(-6) Omega cm and 48 xx 10^(-6) Omega cm ) respectively. Which is the best conductor and why?

When a 40 Vm^(-1) electric field produced inside a conductor then 2 xx 10^(4) Am^(-2) curren density is established in it. Resistivity of the conducot is (1) 2 xx 10^(-3) Omega m (2) 4 xx 10^(-3) Omega m (3) 2 xx 10^(3)Omega m (4) 4 xx 10^(3) Omega m ]\

At what temperature the root mean square velocity is equal to escape velocity from the surface of earth for hydrogen and for oxygen ? Given radius of earth = 6.4 xx 10^(6) m , g = 9.8 ms^(-2) . Boltzmann constant = 1.38 xx 10^(-23) J "molecule"^(-1) .

At what altitude, the acceleration due to gravity reduces to one fourth of its value as that on the surface of the earth ? Take radius of earth as 6.4 xx 10^(6) m , g on the surface of the earth as 9.8 ms^(-2) .

(a) What is meant by saying that the potential difference two points is 1 volt ? Name a device that helps to measure the potential difference across a conductor. (b) Why does the connecting cord of an electric heater not glow hot while the heating element does ? ( c) Electrical resistivities of some substances at 20^@ C are given below : Silver 1.60 xx 10^-8 Omega m Copper 1.62 xx 10^-8 Omega m Tungsten 5.20 xx 10^-8 Omega m Iron 10.0 xx 10^-8 Omega m Mercury 94.0 xx 10^-8 Omega m Nichrome 100 xx 10^-6 Omega m . Answer the following question in relation to them : (i) Among silver and copper, which one is a better conductor ? Why ? (ii) Which material would you advise to be used in electrical heating devices ? Why ?

A conductance cell when filled with 0.5 M KCI solution (conductivity = 6.67 xx 10^(-3) Omega^(-1) cm^(-1) ) register a resistance of 243 Omega . Its cell constant is .

The value of 'g' on the surface of the earth is 9.81 ms^(-2) . Find its value on the surface of the moon . Given mass of earth 6.4 xx 10^(24) kg , radius of earth = 6.4 xx 10^(6) m , mass of the moon = 7.4 xx 10^(22) kg , radius of moon = 1.76 xx 10^(6) m .