A surface charge density of 2.10×10-9 C/cm2 exists on a circle-shaped disc. If the disc's radius increases by a factor of 2 (but the total charge stays the same), what is the surface charge density?

The electric field just above the face of a penny is 1.14×103 N/C. What is the surface charge density on the surface of that penny face?

A point charge causes an electric flux of3 2 12 10 Nm C− to pass through a sphericalGaussian surface of 20.0 cm radius centered on the charge. If the radius of the Gaussiansurface were doubled, how much flux would pass through the surface?

A -8.70 nC charge of mass 1.30×10-6 kg is released from rest 4.20 mm above a very large plane of positive charge. The charge accelerates toward the plane and collides with a speed of 3.20 m/s. What is the surface charge density of the plane? 1.01×10-6 C/m2 2.25×10-7 C/m2 1.61×10-6 C/m2 3.22×10-6 C/m2

A -2.34-nC point charge is located at the center of a conducting spherical shell. The shell has an inner radius of 2.00 m, an outer radius of 4.00 m, and a charge of 8.53-nC. (a) What is the magnitude of the electric field at r = 1.00 m?  N/C (b) What is the magnitude of the electric field at r = 3.00 m?  N/C (c) What is the magnitude of the electric field at r = 5.00 m?  N/C (d) What is the surface charge density, σ, on the outside surface of the shell? (You may enter your calculation using scientific notation.)  C/m2C/m2

a) Derive the expression for the capacitance of a parallel plate capacitor having plate area A and plateseparation d.b) Two charged spherical conductors of radii R1 and R2 when connected by a conducting wire acquire chargesq1and q2 respectively. Find the ratio of their surface charge density in terms of their radii.32. a) Three-point charges, Q1 = +2 μC, Q2 = -3 μC, and Q3 = +4 μC, are placed at the vertices of an equilateraltriangle with sides of length 1 meter. Calculate the net electric field at the center of the triangle.b) A coil is wound around an iron core, and it is connected to a resistor. When the current in the coil ischanged from 2 A to 6 A in 0.2 seconds, an emf of 12 V is induced in the coil. Calculate the self-inductance ofthe coil.33. a) A coil with 200 turns and an area of 0.02 m² is placed in a magnetic field of strength 0.5 T. Calculate themagnetic flux through the coil when it is oriented perpendicular to the magnetic field lines.b) Derive equation of current for R-C circuit