Electric Potential Energy and Electric Potential Physics Topic

Electric Potential Energy and Electric Potential Physics Topic 8 Notes 1 1 of 8 © Boardworks Ltd 2009

Learning Outcomes What is Electric Potential Energy? What is Electric Potential? How is electric potential similar to the universal law of gravitation? How do you calculate electric potential? 2 of 8 9 © Boardworks Ltd 2009

Electric Charge and Work In order to bring two like charges near each other work must be done. In order to separate two opposite charges, work must be done. Remember that whenever work gets done, energy changes form. 3 of 8 9 © Boardworks Ltd 2009

Electric Potential Energy • part of Mechanical Energy • Based on the POSITION of the charges § ME = KE + PEgrav + PEelastic + PEelectric • PEelectric = -q. Ed 4 of 8 9 © Boardworks Ltd 2009

Electric Potential –has many names • AKA: § § § PEelectric /charge Voltage Potential Difference Electric Potential 5 of 8 9 © Boardworks Ltd 2009

Chart Measurement Name Definition Electric Potential Energy EPE The energy due to the position of a charge J J V How energetic charges are V V Electric Potential 6 of 8 9 Units SI Unit © Boardworks Ltd 2009

Electric Potential and Potential Energy Here we see the equation for gravitational potential energy. Instead of gravitational potential energy we are talking about ELECTRIC POTENTIAL ENERGY A charge will be in the field instead of a mass The field will be an ELECTRIC FIELD instead of a gravitational field The displacement is the same in any reference frame and use various symbols Putting it all together! The amount of Question: What does the LEFT side of Energy per the equation mean in words? charge! 7 of 8 9 © Boardworks Ltd 2009

Energy per charge The amount of energy per charge has a specific name and it is called, VOLTAGE or ELECTRIC POTENTIAL (difference). Why the “difference”? 8 of 8 9 © Boardworks Ltd 2009

Equations DV = DPEelectric = -Ed = kq q r 2 Sample Problems: 1. A particle moves 10. 0 m along an electric field of strength 75 N/C, its electrical potential energy decreased by 4. 8 x 10 -16 J. What is the particle’s charge? Step 2: DPEelectric = 4. 8 x 10 -16 J; E = 75 N/C; d = 10. 0 m Steps 3 and 4: q = DPEelectric -Ed Step 5: Step 6: q = - 6. 4 x 10 -19 C 9 of 8 9 © Boardworks Ltd 2009

Equations DV = DPEelectric = -Ed = kq q r 2 Sample Problems: 2. What is the potential difference between the initial and final locations of the particle in Sample 1? Step 2: DPEelectric = 4. 8 x 10 -16 J; E = 75 N/C; d = 10. 0 m Steps 3 and 4: DV = -Ed Step 5: Step 6: DV = -750 V 10 of 8 9 © Boardworks Ltd 2009

Equations DV = DPEelectric = -Ed = kq q r 2 Sample Problems: 3. An electron moves 4. 5 m in the direction of an electric field of 325 N/C. Determine the change in electric potential energy Step 2: q = -1. 6 x 10 -19 C; E = 325 N/C; d = 4. 5 m Steps 3 and 4: DPEelectric = -q. Ed Step 5: Step 6: DPEelectric = 2. 3 x 10 -16 J 11 of 8 9 © Boardworks Ltd 2009

Quiz Question 1 1. 12 of 8 9 © Boardworks Ltd 2009

Quiz Question 2 13 of 8 9 © Boardworks Ltd 2009

Quiz Question 3 14 of 8 9 © Boardworks Ltd 2009