1. How to use Electricity Formulas?

2. Electricity formulas Given on the exam… V=RI P=VI E=P∆t V = Potential difference R = Resistance I = Intensity E = Energy ∆t = Time

3. 5 Steps to formula success 1.What are we looking for? 2.Choose formula (What else are we given?) 3.Rewrite appropriate formula 4.Do we need other formulas? 5.Replace the variables and solve

4. Example 1 1.What are we looking for? - Potential difference (V)

5. Example 1 2. Choose the formula (what are we given?) V=RI P=VI E=P∆t

6. Example 1 3. Rewrite the appropriate formula? V= RI

7. Example 1 4. Do we need another formula? Not in this case

8. Example 1 5. Replace values and solve V = R I V = 25 Ω * 10 A V = 250 V

9. Example 2 1.What are we looking for? - Time (∆t)

10. Example 2 2. Choose the formula (what are we given?) V=RI P=VI E=P∆t

11. Example 2 3. Rewrite the appropriate formula? E= P∆t ∆t = E/P

12. Example 2 4. Do we need another formula? Not in this case

13. Example 2 5. Replace values and solve ∆t = E/P ∆t = 30 000 J / 2000 W ∆t = 15 sec

14. Example 3 1.What are we looking for? - Energy (E)

15. Example 3 2. Choose the formula (what are we given?) V=RI P=VI E=P∆t

16. Example 3 3. Rewrite the appropriate formula? E= P∆t

17. Example 3 4. Do we need another formula? Yes, To only use E=Pt I am missing P I can find it using P=VI

18. Example 3 5. Replace values and solve E = P∆t E = P (30 *60 seconds) P = VI P = 220 V * 50 A P = 11 000 W E = 11 000 W *1800 seconds E = 19 800 000 J (or 5,5 kwH if you use hours instead of seconds

19. Thank you So remember… – Find what we are looking for – Choose your formula or formulas based on the information given to you – Rewrite the formula – Verify if other formulas are needed – Replace the values and solve GOOD LUCK !!!!