Electric Potential and Electric Potential Energy Name___________________________________ Date_________ Hr. ___ To move charged particle in a uniform electric field requires ___________. In other words a force must move over a distance. This will change the ______________ ____________ of the particle in accordance with Charge Q is moved from point A to point B. PEelectric = If the charge is positive its potential energy will decrease because its ability to accelerate is reduced when it is further away from the larger charged particle . + Q A B If the charge is negative its potential energy will increase because its ability to accelerate back towards the larger charged particle increases when it is further away. Two charged particles positioned close together will also have potential energy as they attract or repel each other. Similarly, without involving calculus we can write: PEelectric = It makes more sense to in fact talk about _____________ _______________rather than potential energy. This is because we usually want to know what the effect will be on ________ charge placed in an electric field. This is defined as the amount of potential energy ______ ________ ____________ We can write: V= A potential difference can therefore be defined as: V = If the electric field is uniform: V = Unlike electric field strength, potential and potential energy are both __________ quantities. The potential difference between two points does ______ depend on the ________ taken to move between the two points. Examples 1. A wire is connected to a 9V battery. How much potential energy does each coulomb of charge have that is moving around the conductor? 2. A balloon rubbed on your head can be charged up to 5000V and hold a millionth of a coulomb of charge. How much potential energy does this stored charge have? 3. A classroom Van de Graaff generator can easily be charged up to 50,000 V. Why is touching the dome on the generator not dangerous to a human but sticking your finger in a power outlet at 110 V is? _______________________________________________________________________ _______________________________________________________________________ _______________________________________________________________________ 4. The gap between electrodes in a spark plug is 0.060 cm. To produce an electric spark in a gasoline-air mixture there must be an electric field of 3.0 x 106 V/m. What minimum potential difference must be supplied by the ignition circuit to start a car? 5. In a thunderstorm, the air must be ionized by a high voltage before a conducting path for a lightning bolt can be created. An electric field of about 1.0 x 10 6 V/m is required to ionize dry air. What would the breakdown voltage in air be if a thundercloud were 1.60 km above the ground? Assume that the electric field between the cloud and the ground is uniform.