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Transcript
Ohm’s Law Would this work? 1. 2. Yes No 50% 1 50% 2 Would this work? 1. 2. Yes No 50% 1 50% 2 Would this work? 1. 2. Yes No 50% 1 50% 2 Parts of a circuit (review) Voltage (V): Current (I): Resistance (R): Human circuits activity #1 In your lab groups, build a HUMAN circuit that includes the following: Battery (power source) 3 Light bulbs in SERIES Human circuits activity #2 In your lab groups, build a HUMAN circuit that includes the following: Battery (power source) 3 Light bulbs in PARALLEL Human circuits activity #3 In your lab groups, build a HUMAN circuit that includes the following: Battery (power source) Light bulb Ammeter (to measure current) Voltmeter (to measure voltage) Debrief activity: Measuring voltage: Voltmeter must be placed in PARALLEL with resistor Measuring current: Ammeter must be placed in SERIES If the voltage is increased but the resistance stays the same, what happens to the current? 1. 2. 3. It increases It decreases It stays the same Current is directly proportional to voltage If the resistance is increased but the voltage remains the same, what happens to the current? 1. 2. 3. It increases It decreases It stays the same Current is inversely proportional to resistance So . . . Ohm's law states that the electrical current (I) flowing in an circuit is proportional to the voltage (V) and inversely proportional to the resistance (R). Ohm’s Law Voltage = Current x Resistance V = IR Voltage: measured in Volts (V) Current: measured in Amps (A) Resistance: measured in Ohms (Ω) Practice Problem A lightbulb with resistance of 100 is plugged into a 120 V outlet. What is the current flowing through the bulb? Ohm’s Law Lab Part 1: Part 2: What to do when I finish? 1.) Tidy up lab station and turn in lab to group folder 2.) Go to the PHET website and build various circuits (your choice). You must measure current, voltage, and resistance for each circuit. Draw a circuit diagram and record current, voltage and current. What would the effect be on a person if they stuck their finger into a regular wall outlet that supplies 120V (don’t try this at home) with completely dry skin (R=100,000ohms)? 25% 1. 2. 3. 4. 25% 25% 2 3 25% 12,000,000 Amps 8333 Amps 0.0012 Amps No current 1 4 What would the effect be on a person if they stuck their finger into a regular wall outlet (again don’t try this at home) after sitting in a bathtub full of salt water (R=100ohms)? 25% 1. 2. 3. 4. 25% 25% 2 3 25% 12,000 Amps 1.2 Amps 0.83 Amps No current 1 4