- Practice Problems Here Are Some Practice Problems At A Level That You Might Find On The Final Exam The Final Exam Will 1 (206.22 KiB) Viewed 74 times
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- Practice Problems Here Are Some Practice Problems At A Level That You Might Find On The Final Exam The Final Exam Will 2 (51.11 KiB) Viewed 74 times
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Practice problems Here are some practice problems at a level that you might find on the final exam. The final exam will not contain this many problems and will be structured so that most students can complete it within 30-45 mins. 1. A positron is a fundemental particle with charge q= 1.6 x 10-19 C and mass M = 9.11 x 10-31 kg. It is idential to an electron except that it has the opposite charge. Consider a positron that is released from rest in region A where the potential VA is 27V and allowed to move freely to region B where the potential VB is 7 V. (a) How fast [in m/s] will it be going when it gets to region B? (b) How fast [in m/s) will it be going when it gets to region B if the initial potential VA was instead +10V and the final potential Vg was -10V? (c) If we instead released an electron (q = -1.6 x 10-19 C) from rest at point B, and allowed it to move freely from B to A, what would it's speed be? hint: the answers to parts b and c are the same as part a, and part a is just an application of conservation of potential+kinetic energy. 2. A 120V potential difference is applied to a light bulb which has resistance R = 5002. What current [in Al will flow through the light bulb? hint : Use Ohm's Law 3. Humans have a typical resistance to the flow of electricity between 1 kl to 10 kN, depending on whether the skin is wet or dry and how thick the fat layer is. As a rule of thumb, 1 mA is roughly the lowest current that a typical human can percieve and is experienced as a slight tingling feeling. The 'Let Go threshold is the level of current at which we will begin to lose control of our muscles. For most people this is about 15 mA. Above this level, the current flowing through our muscles interferes with the muscles ability to function. Consider what would happen if you grabbed an exposed 120V household circuit wire and the current flowed through your body to ground. (a) If your skin resistance is at the high end (R=10 k22) what current in mA] will flow through your body? Would this be perceptible to you? Would you be able to 'let go of the wire? (b) If your skin resistance is at the low end (R=1 k 2) - say because you are either wet or standing in a puddle of water, what current [in mA] will flow through your body? Would this be perceptible to you? Would you be able to 'let go of the wire? hint use ohm's law.
C = KEO AQ I= At U = qV ( I(t) = loe-t/t = d = 1 AV = Q А d AU = qAV V(t) = Voe-t/ AV. = € (1-e-t/v) EO =E T= RC I AV R E = + (%) = 1 EO L AV = Ed = = R=PA Ki+Ui Kf+Uf mv + Vi me mu} +qV; 8.85 - 10-12 C2/N·m? Q= CAV Eo