We have been working on Investigating Circuits. Let’s Review… Investigation 12.1 We have been working on Investigating Circuits. Let’s Review… (Notes 12.2 +12.3)

Objective Students will be able to (SWBAT)… relate voltage, current, and resistance.

Voltage A multimeter is used to measure voltage or current, and sometimes resistance. To measure voltage, the meter’s probes are touched to two places in a circuit or across a battery.

A battery uses stored chemical energy to create the voltage difference. If you stack batteries, they add together. Example: Three 1.5-volt batteries can be stacked to make a total voltage of 4.5 volts in a flashlight. Batteries

If you want to measure current, you must force the current to pass through the meter. Multimeters can measure two types of current: alternating current (AC) and direct current (DC). For circuits with light bulbs and batteries, you must set your meter to direct current, or DC Measuring current

Fuses and current The meter used with your electric circuit investigations has a fuse inside. The meter can be damaged or the fuse blown, if too much current passes through it.

Protecting circuits Circuit breakers and fuses are two kinds of devices that protect circuits from too much current by making a break that stops the current.

Describe the picture in your own words.

Resistance Resistance is the measure of how strongly an object resists current flowing through it.

Variable Resistors Potentiometers can be adjusted to have a resistance within a certain range. Example: Dimmer on light or volume switch

Variable Resistors Conductors: carry electric Insulators: do not carry electric Semiconductors: middle level electric flow Technology usually uses both conductors and insulators

Resistance The total amount of resistance in a circuit determines the amount of current in the circuit for a given voltage.

Resistance of common objects A light bulb’s resistance increases when there is more current because the bulb gets hotter when more current passes through it.

Fixed Resistors If you have ever looked at a circuit board inside an electronic device, you may have seen fixed resistors.

Shock! Electrical outlets can be dangerous, but what about batteries? They do not have enough volts to cause damage due to skins resistance. Water can increase chance of shock because it lowers your body’s resistance.

12B Ohm’s Law