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AQA Unit 4 Electric Fields

Whilst doing a Unit 4 question, I came across this,

ImageUploadedByStudent Room1433799628.289082.jpg

Can someone explain a method I could use for doing these sorts of questions?

Thanks,
klaxoii


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Reply 1
You know electric field strength is V/m, and a volt is J/C, so the electric field strength is J/(C*m). This makes the fact that a C is appearing in the numerator of option D look extremely suspicious.

For a more rigorous approach the general idea would be to decompose V/m into SI base units, and decompose each of these options into SI base units. A comparison would then show which units have the same dimension, and which don't, since two units with the same SI base unit decomposition must be equivalent.

That means knowing that C = A/s, J = N*m, N = kg*m/s^2, etc.
Reply 2
Thanks for the reply, I reckon i've got the hang of them now!


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