Technical Theatre Lighting Notes

OHM'S LAW AND GROUNDING

• Ohm's law describes the relationship between voltage (E), current (I), and resistance (R).

  • Formula: $I = \frac{E}{R}$

  • Example:

  • Resistance of human body, $R_{human\ body} = 1000 \ \, \Omega$

  • Ground wire resistance, $R_{ground\ wire} = 1 \ \, \Omega$

  • Voltage (E) = 120 VAC

  • Current calculation: $I = \frac{120 \text{V}}{1000 \Omega} = 0.12\text{ A}$ (or 12 amperes if total voltage is considered).

TRANSFORMERS, AC TRANSMISSION, AND THE POWER LOSS FORMULA

Understanding Transformers

• Power on overhead lines is transmitted at high voltage to increase efficiency and reduce power loss due to resistance.

  • High-voltage electricity = less power loss in long-distance transmission.

• Power Loss Formula:

  • Power loss in a circuit is defined by the formula: $P_{loss} = \frac{P \cdot R}{E}$

  • High voltage leads to lower power loss due to the squaring of voltage in the denominator.

• The current running through transmission lines is typically quite small.

  • Large voltage allows for reasonable power delivery even with small current based on the formula: $P = I \cdot E$.

• Hazard Warning: High voltage power lines are dangerous; extra caution should be exercised around them.

MATHEMATICS OF POWER TRANSMISSION

Example Calculations

• Ground wire circuit example: $I = \frac{120 \text{V}}{1 \Omega} = 120 \text{ A}$.

Power Needs Example

• A power station is situated near coal deposits and needs to supply a city 20 miles away with 120 kW of electrical power.

• Therefore:

  • City Demand: 120 kW

  • Distance: 100,000 feet

Working of Transformers

• Transformers convert high voltage to lower, usable voltage (e.g., stepping down from high voltage to 120 V).

  • Primary Coil: In series with incoming voltage.

  • Secondary Coil: In series with outgoing, adjusted voltage.

• Graphical representation of voltage transformation shows inverse function between primary and secondary voltages over time.

• Components of a transformer include coils of enamel-coated magnet wire and an iron core to optimize magnetic force.

• Insulation Note: Currents of coils are insulated, so there is no direct electrical contact between primary and secondary coils.

Transformer Functionality

• Transformers do not work with direct current (DC); blocking function is utilized in certain audio circuits to protect against static DC. If DC reaches steady state, it neither induces a current nor continues any magnetic field induction in secondary coils.

• Circuit breakers (e.g., 20 A) will trip if excessive current transits through ground wire.

  • Ground wires provide safer alternate paths to resistive loads (human bodies) and help to prevent potentially fatal electrical currents from passing through.

• Grounding Purpose: Ground wires make systems safer but do not guarantee safety.

• Equipment may be double-insulated to prevent shock hazards without requiring grounding.

IMPACT OF WIRE RESISTANCE AND POWER LOSS FORMULAS

• Aluminum wire resistance example is given: $R_{aluminum\ wire} = \frac{10 \Omega}{2\, 1000 \text{ ft}}$.

Power Loss Formula Applications

• Power (P) calculations show that for transformed power values, losses can be calculated.

• Example:

  • Example One: Power loss calculation with known parameters and retrieval of values based on transformers.

UNDERSTANDING TRANSFORMERS AND AC CYCLES

• To fully comprehend transformer operations, it's crucial to understand the AC current that powers them.

• Alternating current (AC) fluctuates, creating a moving magnetic field essential for transformer functionality.

THREE-PHASE POWER AND DISTRIBUTION

Introduction to Three-Phase Power

• Three-phase power is the common polyphase circuit technology that minimizes energy waste while allowing for higher efficiency power generation and distribution.

• Connection Configurations:

  • Wye (Y Connection): Used for standard applications; allows for multiple voltage outputs.

  • Delta: Primarily seen in factories; less common in theatres.

• Each phase in three-phase denotes a different conductor, thus reducing the limitation on system designs and helping share loads.

POWER SYSTEMS COMPONENTS

Components of Power Distribution Systems

• Disconnect boxes and dimmer racks provide the vital bridge between power sources and lighting systems in theaters.

  • Fuses within the disconnect box protect hot legs from overloads.

• Types of wiring may vary; heavier-duty wires (e.g., SO cable) and other connectors (cam locks) are employed for safety due to high power demands.

• Safety Protocols: Always ensure grounding connections are made before other connections to minimize the risk of shock.

SOCKET AND PLUG CONFIGURATIONS

Electrical Connectors

• Various forms of connectors (Edison connectors, cam locks) are vital in linking circuits safely.

  • Note how the color codes for wiring play a key role in how to connect systems safely.

Conclusion

• Understanding electrical theory and distribution, especially in the context of transformers and safe practices with wires and connectors, is vital to prevent accidents and ensure efficient energy use in various settings, particularly in theatrical environments where setups may frequently change.

OHM'S LAW AND GROUNDING

• Ohm's law describes the relationship between voltage (E), current (I), and resistance (R).

  • Formula: $I = \frac{E}{R}$

  • Example:

  • Resistance of human body, $R_{human\ body} = 1000 \ \, \Omega$

  • Ground wire resistance, $R_{ground\ wire} = 1 \ \, \Omega$

  • Voltage (E) = 120 VAC

  • Current calculation: $I = \frac{120 \text{V}}{1000 \Omega} = 0.12\text{ A}$ (or 12 amperes if total voltage is considered).

TRANSFORMERS, AC TRANSMISSION, AND THE POWER LOSS FORMULAUnderstanding Transformers

• Power on overhead lines is transmitted at high voltage to increase efficiency and reduce power loss due to resistance.

  • High-voltage electricity = less power loss in long-distance transmission.

• Power Loss Formula:

  • Power loss in a circuit is defined by the formula: $P_{loss} = \frac{P \cdot R}{E}$

  • High voltage leads to lower power loss due to the squaring of voltage in the denominator.

• The current running through transmission lines is typically quite small.

  • Large voltage allows for reasonable power delivery even with small current based on the formula: $P = I \cdot E$.

• Hazard Warning: High voltage power lines are dangerous; extra caution should be exercised around them.

MATHEMATICS OF POWER TRANSMISSIONExample Calculations

• Ground wire circuit example: $I = \frac{120 \text{V}}{1 \Omega} = 120 \text{ A}$.

Power Needs Example

• A power station is situated near coal deposits and needs to supply a city 20 miles away with 120 kW of electrical power.

• Therefore:

  • City Demand: 120 kW

  • Distance: 100,000 feet

Working of Transformers

• Transformers convert high voltage to lower, usable voltage (e.g., stepping down from high voltage to 120 V).

  • Primary Coil: In series with incoming voltage.

  • Secondary Coil: In series with outgoing, adjusted voltage.

• Graphical representation of voltage transformation shows inverse function between primary and secondary voltages over time.

• Components of a transformer include coils of enamel-coated magnet wire and an iron core to optimize magnetic force.

• Insulation Note: Currents of coils are insulated, so there is no direct electrical contact between primary and secondary coils.

Transformer Functionality

• Transformers do not work with direct current (DC); blocking function is utilized in certain audio circuits to protect against static DC. If DC reaches steady state, it neither induces a current nor continues any magnetic field induction in secondary coils.

• Circuit breakers (e.g., 20 A) will trip if excessive current transits through ground wire.

  • Ground wires provide safer alternate paths to resistive loads (human bodies) and help to prevent potentially fatal electrical currents from passing through.

• Grounding Purpose: Ground wires make systems safer but do not guarantee safety.

• Equipment may be double-insulated to prevent shock hazards without requiring grounding.

IMPACT OF WIRE RESISTANCE AND POWER LOSS FORMULAS

• Aluminum wire resistance example is given: $R_{aluminum\ wire} = \frac{10 \Omega}{2\, 1000 \text{ ft}}$.

Power Loss Formula Applications

• Power (P) calculations show that for transformed power values, losses can be calculated.

• Example:

  • Example One: Power loss calculation with known parameters and retrieval of values based on transformers.

UNDERSTANDING TRANSFORMERS AND AC CYCLES

• To fully comprehend transformer operations, it's crucial to understand the AC current that powers them.

• Alternating current (AC) fluctuates, creating a moving magnetic field essential for transformer functionality.

THREE-PHASE POWER AND DISTRIBUTIONIntroduction to Three-Phase Power

• Three-phase power is the common polyphase circuit technology that minimizes energy waste while allowing for higher efficiency power generation and distribution.

• Connection Configurations:

  • Wye (Y Connection): Used for standard applications; allows for multiple voltage outputs.

  • Delta: Primarily seen in factories; less common in theatres.

• Each phase in three-phase denotes a different conductor, thus reducing the limitation on system designs and helping share loads.

POWER SYSTEMS COMPONENTSComponents of Power Distribution Systems

• Disconnect boxes and dimmer racks provide the vital bridge between power sources and lighting systems in theaters.

  • Fuses within the disconnect box protect hot legs from overloads.

• Types of wiring may vary; heavier-duty wires (e.g., SO cable) and other connectors (cam locks) are employed for safety due to high power demands.

• Safety Protocols: Always ensure grounding connections are made before other connections to minimize the risk of shock.

SOCKET AND PLUG CONFIGURATIONSElectrical Connectors

• Various forms of connectors (Edison connectors, cam locks) are vital in linking circuits safely.

  • Note how the color codes for wiring play a key role in how to connect systems safely.

Conclusion

• Understanding electrical theory and distribution, especially in the context of transformers and safe practices with wires and connectors, is vital to prevent accidents and ensure efficient energy use in various settings, particularly in theatrical environments where setups may frequently change.

Quadrants in Electronics

• Quadrants Defined:

  • Quadrants II and III are not generally used in electronics graphs as they represent times before the origin.

  • Quadrant I: Indicates positive voltage pressure.

  • Quadrant IV: Indicates negative voltage pressure.

Direct Current (DC)

• Definition: DC current is produced when a constant voltage pushes electrons forward in one direction.

• Positive Voltage Pressure: Represented as pushing electrons from the negative terminal to the positive terminal.

Battery Functionality

• Chemical Reactions in Batteries:

  • A chemical reaction occurs between two metals in the battery, facilitated by a catalyst fluid, which provides ions to facilitate electron movement.

  • Common battery composition:

  • Wet cell car battery: Lead and lead dioxide.

  • Rechargeable tool batteries: Nickel and cadmium in a gel.

• High Ion Concentration in Acids:

  • Acids with high ion concentrations act as catalysts, requiring careful handling.

Types of Current1. Direct Current (DC)

• Flow Direction: Electrons flow only in one direction.

• Electrical Characteristics:

  • Produced by batteries.

  • Flow occurs from the negative terminal (collects negatively charged ions) to the positive terminal.

2. Alternating Current (AC)

• Definition: Electrons switch directions periodically, alternating between positive and negative voltage pressures.

• Production Principle: Generated using electromagnetic induction, which will be covered in detail subsequently.

• AC Characteristics:

  • The sinusoidal waveform produces a graph that oscillates above and below the time axis.

Measurement Units1. Amperes (A)

• Definition: One ampere is defined as $6 imes 10^{22}$ electrons moving past a point in one second.

• Function: Measures the amount of current or number of electrons flowing.

2. Volts (V)

• Definition: Measures the pressure used to push electrons through a conductor in a circuit.

3. Ohms (Ω)

• Definition: Measures resistance against the flow of current.

4. Watts (W)

• Definition: Measures electrical power, quantifying how much work is being done.

Ohm's Laws

• Georg Ohm: A physicist who formulated the fundamental laws of electricity in the early 1800s.

• Ohm's First Law:

  • $E = I imes R$

  • Rearrangement gives:

  • $I = E/R$

  • $R = E/I$

• Practical Application: Often used in electrical work, to find unknown values when two are known.

Series Circuits

• Definition: Resistors connected in series share a total voltage divisible among themselves.

• Rules:

  • Total Resistance = Sum of all resistances.

  • Current remains constant throughout all components.

Parallel Circuits

• Definition: Components connected across common points, allowing for different paths for current.

• Rules:

  • Voltage is constant across all branches.

  • The total current is the sum of currents through each branch.

• Example: If multiple devices operate at 120V, they can be connected in parallel without affecting one another.

Sine Wave Characteristics

• AC Waveform Description:

  • Follows a specific curvature known as a sine wave, which represents fluctuations in voltage.

  • Graphically represents how AC voltage ebbs and flows:

    • Positive voltage occurs when peak volts increase during the first half of a cycle and decrease in the second half.

  • The mean voltage measured is the RMS (Root Mean Square).

Electrical Components and Safety

• Wiring and Ratings:

  • Lightbulbs and electrical devices rated for certain wattages to prevent overheating.

  • Use appropriate circuit breakers to protect against overload.

Generators and Power Distribution

• AC Generation Principle: AC is produced through magnetic induction, correlating the motion of wire coils within a magnetic field to generate current.

• Power Grids: Efficiently connect power stations to handle varying demands and ensure consistent electricity supply

Capacitors and Electrons

• Capacitor Functionality: Capacitors store electrons temporarily based on circuit voltage pressure and release them as needed during varying circuit conditions.

Safety Measures

• Current Shock Risks: Grounded circuits prevent accidental electrocution; safety when working near wet areas or conductive materials is crucial.

Voltage Pressure and Acidity in Circuits

• Acids in Circuits: Careful handling of acid-based batteries is critical to prevent leaks and other hazards.