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1) Two infinitely long charged cylinders are centered on the same axis. The inne

ID: 1767793 • Letter: 1

Question

1) Two infinitely long charged cylinders are centered on the same axis. The inner cylinder of radius a=3cm has a uniform linear charge density n=4.00E-10 C/m along the axis. The outer cylinder of radius b =6 cm has a uniform linear charge density -n along the axis. What is the electric potential difference between the two cylinders?


___ Volts



2?As the figure 1 shows, a ring has uniform linear charge density m=2.00E-10 C/m, the radius is R=10 cm. What is the potential at P on the central perpendicular axis through the ring? (the distance between P and the center is Z=50 cm)


___ Volts

Two infinitely long charged cylinders are centered on the same axis. The inner cylinder of radius a=3cm has a uniform linear charge density n=4.00E-10 C/m along the axis. The outer cylinder of radius b =6 cm has a uniform linear charge density -n along the axis. What is the electric potential difference between the two cylinders? 2?As the figure 1 shows, a ring has uniform linear charge density m=2.00E-10 C/m, the radius is R=10 cm. What is the potential at P on the central perpendicular axis through the ring? (the distance between P and the center is Z=50 cm)

Explanation / Answer

1)

The electric field between the cylinders is:

E = (n)/(2 pi r epsilon0)

E = (4e-10)/(2*3.1416*8.85e-12*r)

E = 7.1934/r

So

V = int{-E.dr}

V = int{-(7.1934/r) dr}

V = -(7.1934) Ln(r)

the electric potential difference between the two cylinders:

dV = -(7.1934) (Ln(0.03) - Ln(0.06))

dV = -(7.1934) (Ln(0.03/0.06))

dV = -(7.1934) (-0.69315)

dV = 4.99 Volts


2)

Q = m (2 pi R) = 2e-10 * (2*3.1416*0.10) = 0.000000000125664 C

V = k Q/sqrt(R^2 + z^2) = 9e9*0.000000000125664/(0.10*0.10+0.50*0.50)y0.5 = 2.218 Volts