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# A2 Electric Fields Past Paper Question watch

1. Hello, would appreciate help with this question:

+.A -.B
<----------------------------------------->
8x10^-10m

Figure 1 shows two point charges of equal magnistude, 1.6x10^-19 and opposite sign, held a distance 8x10^-10m apart at points A and B. The charge at A is positive.

Calculate the magnitude of the electric field strength at the mid point between the charges. Give a suitable unit for your answer.

Oops. Realised my diagram came out wrong. But its explained in question

I think the answer in markscheme was 1.8x10^10 N C^-1

Can't get to that. I end up getting to 9x10^9, which if I multipy by two gives the correct answer. But makes no sense.

Thanks
2. (Original post by ViolinGirl)
Hello, would appreciate help with this question:

+.A -.B
<----------------------------------------->
8x10^-10m

Figure 1 shows two point charges of equal magnistude, 1.6x10^-19 and opposite sign, held a distance 8x10^-10m apart at points A and B. The charge at A is positive.

Calculate the magnitude of the electric field strength at the mid point between the charges. Give a suitable unit for your answer.

Oops. Realised my diagram came out wrong. But its explained in question

I think the answer in markscheme was 1.8x10^10 N C^-1

Can't get to that. I end up getting to 9x10^9, which if I multipy by two gives the correct answer. But makes no sense.

Thanks
F= kq1q2/r2
=> E= f/q = kq/r^2 =)
3. (Original post by ViolinGirl)
Hello, would appreciate help with this question:

+.A -.B
<----------------------------------------->
8x10^-10m

Figure 1 shows two point charges of equal magnistude, 1.6x10^-19 and opposite sign, held a distance 8x10^-10m apart at points A and B. The charge at A is positive.

Calculate the magnitude of the electric field strength at the mid point between the charges. Give a suitable unit for your answer.

Oops. Realised my diagram came out wrong. But its explained in question

I think the answer in markscheme was 1.8x10^10 N C^-1

Can't get to that. I end up getting to 9x10^9, which if I multipy by two gives the correct answer. But makes no sense.

Thanks
post your working so we could see where youre going wrong
4. (Original post by ViolinGirl)
.
Electric Field Strength is a vector. Each charged particle exerts an electric field, so just use the formula for radial field strength and add them together. Remember that their directions will be the same (hence you sum them) because their charges are opposite (so a +ve charge would be forced to the same direction by each field).

Hope that helps

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