Talk:A-level Physics/Forces, Fields and Energy/Electric fields

Specification
From the OCR GCE Physics A specification. Tick with &#10004; when you feel each part of the specification has been covered. Try not to add much more than what is in this list as it would not appear in the exam anyway. Use links to wikipedia for more depth in a topic.


 * 1) Understand an electric field as an example of a field of force and define, recall and use electric field strength as force per unit positive charge. &#10004;
 * 2) Use field lines to represent an electric field. &#10004;
 * 3) Recall and use Coulomb’s law for point charges in a vacuum in the form F = kQ1Q2 / r 2, where k = 1 / 4πε0. &#10004;
 * 4) Recall and use E = kQ / r 2 for the electric field strength of a point charge. &#10004;
 * 5) Recall and use E = V/d for the magnitude of the uniform electric field strength between charged parallel plates. &#10004;
 * 6) Recognise the similarities of, and differences between, electric fields and gravitational fields. &#10004;

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I dunno how to discuss stuff in a wiki manner so ill just add it here. the bit about electric potential and the work required to move it seem to be described in the same way, give the same restult, yet the formula is different        W = k Q1Q2/r          &  V =k  Q/r  supposed to give the work required?? but one includes another charge

=Temporarily moved from the article page= I'm not sure how this exactly fits in, there's no explanation, and it doesn't directly follow on from the previous section (it was placed just before the "differences and similarities of fields". I'm leaving it here until I know what to do with it. Krackpipe (discuss • contribs) 11:07, 19 April 2011 (UTC)

Electric Potential and Work
Electric Potential is defined as the work that must be done to bring unit charge from infinity to a point in an electric field, a distance r from the center of the charge causing the field.




 * $${V}$$
 * $$= \frac {1} {4\pi\epsilon_0} \times \frac {Q} {r}$$
 * $$ = \frac {Q} {4\pi\epsilon_0 r}$$
 * }
 * $$ = \frac {Q} {4\pi\epsilon_0 r}$$
 * }

The electric field strength at the point where the unit charge is, is equal to the negative potential gradient at that point.




 * $${E}$$
 * $$=-\frac {dV} {dr}$$
 * $$= -\frac{d}{dr} \left( \frac {Q} {4\pi\epsilon_0 r} \right)$$
 * $$= -\frac {Q} {4\pi\epsilon_0} \times \frac{d}{dr} \left( \frac{1}{r} \right)$$
 * $$= \frac {Q} {4\pi\epsilon_0} \times \frac{1}{r^2}$$
 * $$= \frac {Q} {4\pi\epsilon_0 r^2}$$
 * }
 * $$= -\frac {Q} {4\pi\epsilon_0} \times \frac{d}{dr} \left( \frac{1}{r} \right)$$
 * $$= \frac {Q} {4\pi\epsilon_0} \times \frac{1}{r^2}$$
 * $$= \frac {Q} {4\pi\epsilon_0 r^2}$$
 * }
 * $$= \frac {Q} {4\pi\epsilon_0} \times \frac{1}{r^2}$$
 * $$= \frac {Q} {4\pi\epsilon_0 r^2}$$
 * }
 * $$= \frac {Q} {4\pi\epsilon_0 r^2}$$
 * }

Electric Potential Energy is defined as the work that must be done to bring a specific charge from infinity to a point in an electric field, a distance r from the centre of the charge causing the field.




 * $${U}$$
 * $$= \frac {1} {4\pi\epsilon_0} \times \frac {Q_1 Q_2} {r}$$
 * $$ = \frac {Q_1 Q_2} {4\pi\epsilon_0 r}$$
 * $$ ={Q_2 V}$$
 * }
 * $$ ={Q_2 V}$$
 * }
 * $$ ={Q_2 V}$$
 * }

The electric force acting on the charge is equal to the negative potential energy gradient at that point.


 * $${F}$$
 * $$=-\frac {dU} {dr}$$
 * $$= -\frac{d}{dr} \left( \frac {Q_1 Q_2} {4\pi\epsilon_0 r} \right)$$
 * $$= -\frac {Q_1 Q_2} {4\pi\epsilon_0} \times \frac{d}{dr} \left( \frac{1}{r} \right)$$
 * $$= \frac {Q_1 Q_2} {4\pi\epsilon_0} \times \frac{1}{r^2}$$
 * $$= \frac {Q_1 Q_2} {4\pi\epsilon_0 r^2}$$
 * }
 * $$= -\frac {Q_1 Q_2} {4\pi\epsilon_0} \times \frac{d}{dr} \left( \frac{1}{r} \right)$$
 * $$= \frac {Q_1 Q_2} {4\pi\epsilon_0} \times \frac{1}{r^2}$$
 * $$= \frac {Q_1 Q_2} {4\pi\epsilon_0 r^2}$$
 * }
 * $$= \frac {Q_1 Q_2} {4\pi\epsilon_0} \times \frac{1}{r^2}$$
 * $$= \frac {Q_1 Q_2} {4\pi\epsilon_0 r^2}$$
 * }
 * $$= \frac {Q_1 Q_2} {4\pi\epsilon_0 r^2}$$
 * }

Electric potential energy and electric potential
120.60.16.100 (discuss) 09:34, 22 August 2012 (UTC)No information on both of them120.60.16.100 (discuss) 09:34, 22 August 2012 (UTC)