Electricity and Magnetism Answers

1)Two-point charges q1=+9μC and q2=−4μC are separated by a distance L =10 cm, see Fig. below. Find the point at which the resultant electric field is zero.

2)Two identical small spheres of mass m and charge q hang from non-conducting strings, each of length L. At equilibrium, each string makes an angle θ with the vertical, see Fig. below (a) When θ is so small that tanθ ≈ sin θ, show that the separation distance r between the spheres is 𝑟=(𝐿𝑞2/2𝜋𝜖0𝑚𝑔)13. (b) If L =10 cm, m=2 g, and r =1.7 cm, what is the value of q?

An ion with a charge of +3.2 × 10–19 C and a mass of 2.7 × 10–26 kg is moving due south at a speed of 4.8 × 103 m s–1 . It enters a uniform magnetic !eld of strength 4.6 × 10–4 T directed downwards towards the ground. Determine the force acting on the ion. 

A straight wire of length 0.75 m carries a current of 35 A. The wire is at right angles to a magnetic field of strength 0.058 T. Calculate the force on the wire.

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The earth revieved about 1300W/m^2 energy from the sun. Assuming the energy to be in the form of plane polarized monochromatic waves and assuming Normal incidence, calculate

1. The magnitude of the electric filed vector

2. The magnitude of the magnetic field vector

What is the boundary condition for H between two dielectric media (with no free charge and no conduction current)?

Write down the general expression for Poynting’s vector

A plane electromagnetic wave of angular frequency ω and wave number k propagates in a vacuum in the negative x direction. The electric field of the wave is linearly polarised in the y direction. Write down an appropriate expression for the wave electric field.

Please write down Faraday’s Law and Ampere-Maxwell’s equation for time-dependent electromagnetic fields in a medium.