Rotating E-Field

Electricity and Magnetism Level 3

Two charges $Q_1$ and $Q_2$ are fixed in place at equal distances from the origin. $Q_1$ is on the negative $x$ axis, and $Q_2$ is on the negative $y$ axis. The charge values vary over time as shown.

Is the magnitude of the net electric field at the origin constant or variable? And does the field rotate clockwise or anticlockwise?

Note: Use the convention that the field from a positive charge points outward from the charge.

constant / anticlockwise variable / anticlockwise variable / clockwise constant / clockwise

1 solution

Jonas Mantek
Jun 16, 2019

The electric field vector at the origin would be proportional to $\cos{t}$ in its x-component and $\sin{t}$ in its y-component. Its magnitude is therefore proportional to $\sqrt{ cos^2(t) + sin^2(t) }$ , which is just 1, meaning constant. At $t = 0$ it is apparent that the vector would point directly to the right, but since $\sin{t}$ will increase from this point and $\cos{t}$ will decrease, the field rotates anticlockwise with $t$ .

Rotating E-Field

1 solution

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