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PowerPoint ® Presentation Chapter 4 The Simple Circuit and Ohms Law Conductors Switches Switch Characteristics Loads Overcurrent Overcurrent Protection Devices Voltage and Current Measurements DC Voltage Measurements DC Current Measurements Ohms Law Determining Current Determining Voltage Determining Resistance Determining Power

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Chapter 4 The Simple Circuit and Ohms Law An electrical circuit consists of a voltage source, insulated conductors, a load, a switch, and a fuse.

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Chapter 4 The Simple Circuit and Ohms Law In a schematic or wiring diagram, conductors are shown as lines. Conductors that are connected often use a dot to indicate the connection.

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Chapter 4 The Simple Circuit and Ohms Law Switches are control devices and are used to close and open circuits safely.

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Chapter 4 The Simple Circuit and Ohms Law The position of the contacts, number of poles, number of throws, and type of break are used to describe switch contacts.

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Chapter 4 The Simple Circuit and Ohms Law Switches are available in many shapes and are often designated according to their use.

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Chapter 4 The Simple Circuit and Ohms Law Common lighting circuit switches include two- way, three-way, and four- way switches.

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Chapter 4 The Simple Circuit and Ohms Law Rotary switches are used to connect multiple positions to a single pole.

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Chapter 4 The Simple Circuit and Ohms Law Loads convert electrical energy to another form of energy such as motion, light, heat, or sound.

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Chapter 4 The Simple Circuit and Ohms Law A short circuit has a resistance that is lower than the normal circuit resistance.

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Chapter 4 The Simple Circuit and Ohms Law Overcurrent protection devices such as fuses are used to protect a circuit from a short circuit or overcurrent that can cause circuit damage.

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Chapter 4 The Simple Circuit and Ohms Law Cartridge and plug fuses may be surrounded with glass or encased in a composite material to suppress an arc or flame.

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Chapter 4 The Simple Circuit and Ohms Law A circuit breaker is an overcurrent protective device that does not need to be replaced each time the circuit current rating is exceeded. Circuit breakers may be thermally or magnetically operated.

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Chapter 4 The Simple Circuit and Ohms Law Thermal circuit breakers use a bimetallic strip attached to a latch mechanism to open the circuit when a short circuit or overload occurs.

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Chapter 4 The Simple Circuit and Ohms Law Magnetic circuit breakers use an electromagnet coil and armature to open the circuit when a short circuit or overload occurs.

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Chapter 4 The Simple Circuit and Ohms Law Thermal overload relay contacts open when the current level is exceeded for a given period of time. The temperature rise in the metal frame of the motor is used to heat the bimetallic strip.

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Chapter 4 The Simple Circuit and Ohms Law In a standard motor control circuit, a relay coil controls a set of normally open contacts and a set of normally closed overload relay contacts.

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Chapter 4 The Simple Circuit and Ohms Law DC voltage measurements using a digital multimeter are taken by connecting the black test lead to the negative polarity test point and the red test lead to the positive polarity test point.

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Chapter 4 The Simple Circuit and Ohms Law DC voltage is measured with an analog meter using standard procedures.

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Chapter 4 The Simple Circuit and Ohms Law To measure current flow through a component, a meter must be connected so that the total electron flow is through the meter circuit.

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Chapter 4 The Simple Circuit and Ohms Law DC current is measured with an analog multimeter using standard procedures.

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Chapter 4 The Simple Circuit and Ohms Law Clamp-on ammeters measure current by measuring the strength of the magnetic field around a single conductor.

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Chapter 4 The Simple Circuit and Ohms Law Ohms law is the relationship between voltage, current, and resistance in an electrical circuit.

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Chapter 4 The Simple Circuit and Ohms Law Current in a circuit increases with an increase in voltage and decreases with an increase in resistance.

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Chapter 4 The Simple Circuit and Ohms Law Voltage in a circuit increases with an increase in current and increases with an increase in resistance.

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Chapter 4 The Simple Circuit and Ohms Law Resistance in a circuit increases with an increase in voltage and decreases with an increase in current.

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Chapter 4 The Simple Circuit and Ohms Law The power formula is the relationship between power, voltage, and current in an electrical circuit.

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Chapter 4 The Simple Circuit and Ohms Law Power in an electrical circuit is calculated by multiplying current by voltage.

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Chapter 4 The Simple Circuit and Ohms Law Power in an electrical circuit calculated by multiplying current squared by resistance.

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Chapter 4 The Simple Circuit and Ohms Law Power in an electrical circuit can be calculated by dividing voltage squared by resistance.

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