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प्रश्न
Welders wear special goggles or face masks with glass windows to protect their eyes from electromagnetic radiations. Name the radiations and write the range of their frequency.
उत्तर
Welders wear special goggles with glass windows to protect the eyes from Ultra Violet rays (UV rays). The range of UV rays is 4×10-7 m (400 nm) to 6×10-10 m (0.6 nm).
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संबंधित प्रश्न
Electric field intensity in free space at a distance ‘r’ outside the charged conducting sphere of radius ‘R’ in terms of surface charge density ‘ a ’ is............................
(a)`sigma / in_0[R/r]^2`
(b)`in_0/sigma[R/r]^2`
(c)`R/r[sigma/in_0]^2`
(d)`R/sigma[r/in_0]^2`
A metal rod `1/sqrtpi `m long rotates about one of its ends perpendicular to a plane whose magnetic induction is 4 x 10-3 T. Calculate the number of revolutions made by the rod per second if the e.m.f. induced between the ends of the rod is 16 mV.
Prove theoretically (electromagnetic induction) `e = (dphi)/(dt)`
Name and state the law which determines the direction of induced current.
or
State Fleming’s right-hand rule.
Consider the energy density in a solenoid at its centre and that near its ends. Which of the two is greater?
Why soft iron is preferred to be used as the core of the electromagnet of an electric bell?
A straight metal wire crosses a magnetic field of flux 4 mWb in a time 0.4 s. Find the magnitude of the emf induced in the wire.
A coil of 200 turns carries a current of 0.4 A. If the magnetic flux of 4 mWb is linked with each turn of the coil, find the inductance of the coil.
Name some equipment that uses electromagnetism for functioning.
One solenoid is centered inside another. The outer one has a length of 50.0 cm and contains 6750 coils, while the coaxial inner solenoid is 3.0 cm long and π cm2 in area and contains 150 coils. The current in the outer solenoid is changing at 3000 A/s. The emf induced in the inner solenoid is ______ V.
(Round off to two decimal places.)
