Points A and B lie within a region of space where there is a uniform electric field that has no x- or z-component; only the y-component Ey is non zero. Point A is at y=8.00 cm and point B is at y=15.0 cm. The potential difference between B and A is VB−VA=+12.0 V, so point B is at higher potential than point A. (a) Is Ey positive or negative? (b) What is the magnitude of the electric field? (c) Point C has coordinates x=5.00 cm, y=5.00 cm. What is the potential difference between points B and C?

Respuesta :

Answer:

(a) Ey is negative

(b) The magnitude of the electric field is E = 171.429 V/m

(c) The potential difference between points B and C is 17.1429 V

Explanation:

(a) Here, we have the potentials given by;

[tex]V_A - V_B = +12.0V[/tex] with point A at y = 8.00 cm and point B at point y = 15.0 cm

where point B is at a higher potential than point A, that is the electric potential is from;

B with y = 15.0 cm to A with y = 8.0 cm which means

[tex]E_y[/tex] decreases as y increases or [tex]E_y[/tex]  is negative.

(b) The magnitude of the electric field is given by

The work done to move a charge from B to A is

[tex]W_{BA} = - \Delta U[/tex] where

[tex]\Delta U = U_a -U_b = q_0E(y_b-y_a)[/tex]

[tex]V_{BA} = \frac{\Delta U}{q_0} = \frac{q_0E(y_b-y_a)}{q_0} = E(y_b-y_a)[/tex]

∴ [tex]E = \frac{V_{BA}}{(y_b-y_a)}[/tex]

[tex]E = \frac{12 \hspace{0.09cm}V}{(0.015\hspace{0.09cm} m -0.008\hspace{0.09cm} m)}[/tex]

E = 171.429 V/m

(c) Here we have point C x = 5.00 cm and y = 5.00 cm

Therefore we have the distance from B to C given by

[tex]y_b-y_c = 15.00 \hspace{0.09cm}cm - 5.00 \hspace{0.09cm}cm = 10.00 \hspace{0.09cm} cm[/tex]

Where 10.00 cm = 0.01 m

E = V/Δy

Therefore, V = Δy·E

For [tex]V_{BC}[/tex], Δy = [tex]y_b-y_c = 0.01 \hspace{0.09cm} m[/tex] and we have,

[tex]V_{BC} = E\times (y_b-y_c)[/tex]

[tex]V_{BC} = 171.429\times (0.015-0.005) = 17.1429\hspace{0.09cm}V[/tex]

(a) The electric field is negative.

(b) The magnitude of the electric field is 1.71 V/m

(c) The potential difference between point B and C is 17.1 V

Given that the electric field has only y-component. Point A and B are at 8cm and 15 cm respectively on y-axis.points

Potential Difference:

(a) The potential difference is given by:

[tex]E=-\frac{\Delta V}{\Delta r}[/tex]

Here [tex]\Delta V[/tex] is positive and [tex]\Delta r=15-8=7cm[/tex] is also positive, therefore [tex]E[/tex]must be negative.

(b)The magnitude of the electric field:

[tex]E=-\frac{\Delta V}{\Delta r}=-\frac{12}{7}V/m=-1.71V/m[/tex]

Thus the magnitude of the electric field is 1.71 V/m

(c) Only the Y coordinate of point C will be considered since the electric field is in y-direction only.

So, [tex]\Delta V_{BC}=-E\Delta r=-(-1.71)(15-5)V=17.1 V[/tex]

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