An insulating rod is placed on y axis as shown. One half is uniformly charged with a positive charge +Q, the other half is uniformly charged with a negative charge -Q (see Figure). The potential is defined to be zero at infinity. At the point P shown on the x-axis we can conclude. Qu4-Pic2-UP2-2020

Question

The electric field and potential are both zero
The electric field is zero but the potential is non zero
The potential and the electric field are both non zero
The potential is non zero but the electric field is up
The potential is zero but the electric field is down
The potential is zero but the electric field is to the left
The potential is zero but the electric field is to the right

Answer 1

When analyzing the situation with the insulating rod charged +Q on one half and -Q on the other half, we can summarize the effects of both the electric field and electric potential at point P on the x-axis.

Electric Field

1. The electric field produced by a positive charge (+Q) points away from that charge, while the electric field produced by a negative charge (-Q) points toward that charge.
2. Therefore, at point P, you would have:
   • The electric field due to the positively charged half of the rod pushing away from the rod (to the right).
   • The electric field due to the negatively charged half pulling towards the rod (to the left).

Since point P is equidistant from both charges, the magnitudes of the electric fields due to each half (positive and negative) will be equal, but they will point in opposite directions. Thus, the total electric field at point P will be zero.

Electric Potential

1. The electric potential due to a positive charge is positive and increases as you get closer, while the potential due to a negative charge is negative and decreases as you get closer.
2. Referring to the contributions to the potential at point P:
   • The positive charge contributes a positive potential that is greater than zero.
   • The negative charge contributes a negative potential which is less than zero.

At point P, these potentials do not cancel each other out, meaning the total electric potential at point P is non-zero.

Conclusion

Thus, at point P:

• The electric field is zero.
• The potential is non-zero.

So the correct answer is: The electric field is zero but the potential is non-zero.