Throughout a region of space, the electric field is zero. What can you tell abou

Question

Throughout a region of space, the electric field is zero. What can you tell about the voltage there? It is zero. It is constant in time. It is uniform in space. None of the above Calculate the final speed of an electron that is accelerated from rest through a voltage of 240V. Suppose that the voltage at x = 3m is V = - 20V, while at x = 5m, V = + 30V. Determine the average electric field in this region, both strength and direction. Air breaks down and allows sparks to pass through it once it experiences a field stronger than 3MV/m. Therefore a 40 cm diameter van de Graaff generator will spark if too much charge is placed on its dome. What is the maximum charge it can hold? What is the maximum voltage of the dome?

Explanation / Answer

1)

the relation between electric field and potential difference ( voltage) is E = dV/dr

dV/dr = E

given that E = 0

dV/dr = 0

this is possible only when Voltage is constant

so the answer is B) it is constant in time

2) Work done through a potential difference = change in kiinetic energy

q*dV = Final KE - initial KE

q is the charge of electron = 1.6*10^-19 C

dV = 240 V

final KE = 0.5*m*V^2

m is the mass of electron

V = final speed = ?

then

initial KE = 0.5*m*u^2 = 0 since initial speed u is zero (i.e rest)

then

q*dV = 0.5*m*(v^2-u^2)

1.6*10^-19*240 = 0.5*9.11*10^-31*(v^2-0^2)

v = 9.18*10^6 m/sec is the final speed of electron

Related Questions

Navigate

• Browse (All)
• Browse T
• Subjects

---

---

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.