AP EAMCET2010PhysicsMagnetic Effects of Current
In Thomson's experiment to determine e m of an electron, it is found that an electron beam having a kinetic energy of 45.5 eV remains undeflected, when subjected to crossed electric and magnetic fields. If E=1 10^3 Vm ⁻¹ , the value of B is (mass of the electron is 9.1 10⁻³¹ ~kg )
Options
- A2.5 10⁻³ ~Wb ~m ⁻²
- B5.0 10⁻⁴ ~Wb ~m ⁻²
- C2.5 10⁻⁴ ~Wb ~m ⁻²
- D1.0 10⁻⁴ ~Wb ~m ⁻²
Correct answer
C. 2.5 10⁻⁴ ~Wb ~m ⁻²
Step-by-step solution
The kinetic energy K= 1 2 m v^2v^2= 2 K m v^2= 2 45.5 1.6 10⁻¹⁹ 9.1 10⁻³¹ v^2=16 10¹²v=4 10^6 Again velocity, v= E B 4 10^6= 1 10^3 B B= 1 10^3 4 10^6 B=2.5 10⁻⁴ ~Wb ~m ⁻²