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Electronics Merit Badge Class 2

Electronics Merit Badge Class 2. Resistance. Resistance is an electrical property of a material that “resists” the flow of electrons. The schematic symbol for a resistor is: Common units for resistance are: Ohms Kilohm: 1K= 1000 ohms, 10K = 10,000 ohms Megohm: 1M = 1,000,000 ohms

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Electronics Merit Badge Class 2

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  1. Electronics Merit Badge Class 2 Electronics Merit Badge Class 2

  2. Resistance • Resistance is an electrical property of a material that “resists” the flow of electrons. • The schematic symbol for a resistor is: • Common units for resistance are: • Ohms • Kilohm: 1K= 1000 ohms, 10K = 10,000 ohms • Megohm: 1M = 1,000,000 ohms • The units symbol for ohms is: Ω (ohms) Electronics Merit Badge Class 2

  3. Current • Current: Defined as “flow of electrons”. • Current: Units of current is AMPS. • Current: Electrical symbol for current is I. • Common units for current are: • Amps • Milliamps (ma): 1 ma = .001 amp • Microamps (ua) : 1 ua = .000001 amp, or .001 ma • Nanoamps (na) : 1 na = .000000001 amp or .000001 ma, or .001 ua. Electronics Merit Badge Class 2

  4. Voltage • Volts is the electrical force that causes electrons (current) to flow. • Units of volts is VOLTS. • The symbol of volts is E or V. We will use V. • Common units for voltage are: • Volts • Millivolt (mv) : .001 volt. • Microvolt (uv) : .000001 volt, or .001 mv • Nanovolt (nv) : .000000001 volt, or .000001 mv, or .001 uv. Electronics Merit Badge Class 2

  5. Ohms Law One of the most important laws in electronics/electricity. V = I x R : Voltage = Current x Resistance Volts is measure in VOLTS, current is measured in AMPS, and resistance is measured in OHMS. 1 AMP, going through 1 OHM of resistance, generates a voltage drop of 1 VOLT. 1 V = 1 A x 1 Ω. Electronics Merit Badge Class 2

  6. More Ohm’s Law Different forms of Ohm’s Law: V = I x R : Voltage = Current X Resistance I = V / R : Current = Voltage / Resistance R = V / I : Resistance = Voltage / Current Volts = 10. Resistance = 1000Ω Compute current. I = V / R I = 10 / 1000 = .01A .01A = 10ma Question: what would the current be if the voltage was 1 V? How about 1000 V? + 10V 1000 Ω Electronics Merit Badge Class 2

  7. Ohm’s Law Exercise Using a meter, we will measure some resistors. Then, using ohm’s law, we will calculate the resistor’s values. To do this, we will use the meter to measure current and voltage in a circuit. Electronics Merit Badge Class 2

  8. Ohms Law – Step 1 Meter 000 + - SET METER TO DCA -20m A Using the meter, measure current. I = _________ amps B

  9. Ohms Law – Step 2 Meter 000 SET METER TO DCV - 20 Using the meter, measure voltage. V = _________ volts

  10. Ohms Law – Step 3 Calculate resistance from your 2 measurements. Ohms Law : V = I x R. Therefore, R = V / I <- Use this equation. Note: you will be measuring current on the 20ma range, so a value of 2.5ma needs to be written as .0025A when using this equation.

  11. Ohms Law – Step 4 Meter 000 SET METER TO Ω – 20k Using the meter, measure Resistance. R = _________ ohms How does this compare with your calculated value?

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