Name:_____MrsDunn_________ Ohm’s Law Practise Worksheet Part A (Reference - http://mrsganske.wikispaces.com/2012-13+Physical+Science+Term+2A ) Show all four steps for each problem STEP 1 - WRITE EQUATION STEP 2 – RE-ARRANGE EQUATION IF NEEDED STEP 3 - SUBSTITUTE IN THE EQUATION STEP 4 – SOLVE 1. Find the current through a 12-ohm resistive circuit when 24 volts is applied. I = V/R = 24/12 = 2A 2. Find the resistance of a circuit that draws 0.06 amperes with 12 volts applied. R=V/I = 12/0.06 = 200 Ω or 200 Ohm 3. Find the applied voltage of a circuit that draws 0.2 amperes through a 4800-ohm resistance. V=IR =0.2*4800 = 960V 4. Find the applied voltage of a telephone circuit that draws 0.017amperes through a resistance of 15,000 ohms. V = IR = 0.017x 15000 = 255V 5. A 20-volt relay has a coil resistance of 200 ohms. How much current does it draw? I = V/R = 20/200 = 0.1A 6. A series circuit has 1200-ohms of total resistance with 12 V as the power supply. What is the total current of this circuit? I = V/R = 12/1200 = 0.01A 7. A transformer is connected to 120 volts. Find the current if the resistance is 480-ohms? I = V/R = 120/480 = 0.25A 8. A resistive load of 600-ohms is connected to a 24 V power supply. Find the current through the resistor. I = V/R = 24/600 = 0.04A 9. A circuit consists of a 12 V battery connected across a single resistor. If the current in the circuit is 3 A, calculate the size of the resistor. R = V/I = 12/3 = 4 Ohm 10. What is the increase of current when 15 V is applied to 10000-ohm rheostat, which is adjusted to 1000ohm value? I = V/R I1 = 15/10000 = 0.015A = 15mA I2 = 15/1000 = 0.0015A =1.5mA Difference or Increase = 15-1.5 = 13.5mA = 0.0135A Part B (Reference - http://www.allaboutcircuits.com/worksheets/ohm_law.html) 1. Explain, step by step, how to calculate the amount of current (I) that will go through the resistor in this circuit: Ohm’s Law I=V/R = 12/470 = 0.0255A = 25.5mA 2. What is the value of this resistor, in ohms (Ω)? R=V/I = 12.3/4.556 = 2699.7 Ohm = 2K7 Ohm 3. A common saying about electricity is that it always takes the path of least resistance." Explain how this proverb relates to the following circuit, where electric current from the battery encounters two alternate paths, one being less resistive than the other: I1 = V/R = 10/250 = 40mA I2 = V/R = 10/800 = 12.5mA I1-I2 = 40 - 12.5 = 37.5mA The current through the 250Ohm resistor is more. 4. What would happen if a wire having no resistance at all (0 Ω) were connected directly across the terminals of a 6-volt battery? How much current would result, according to Ohm's Law? I = V/R =6/0 Heat up, Short circuit