Electricity and Circuits Lecture Notes

Flashcards based on lecture notes about electricity, static electricity, circuits, and related concepts.

What makes an object neutral?

When an object contains an equal number of protons and electrons.

What characterizes a positively charged object?

An excess of protons (lost electrons).

What characterizes a negatively charged object?

An excess of electrons (gained electrons).

What are the key points of the electron theory?

Matter is made up of atoms; two types of charges exist (positive and negative); outer electrons in a solid can move around.

What factors affect internal resistance?

Type of material, cross-sectional area, length, and temperature.

How does resistance affect electron flow?

Materials with lower resistance allow electrons to pass through easily.

How does the thickness of a wire affect resistance?

Thin wires have higher resistance due to less room for electron movement.

How does the length of a wire affect resistance?

Long wires have higher resistance because electrons have to work for a longer time.

How does temperature affect resistance?

As temperature increases, particles move more, making it harder for electrons to move through the wire.

What unit is resistance measured in?

Ohms (Ω).

How is resistance calculated according to Ohm's Law?

Potential difference / Current.

What is the formula for calculating potential difference (voltage)?

V = IR.

What is the potential difference across a light bulb with a resistance of 144 Ω and a current of 0.833A?

120V.

What is static electricity?

A buildup of charge in one area that does not move or flow.

What are the methods of building up static charges?

Charging by friction, conduction, and induction.

How do materials become charged when rubbed together?

The material that loses electrons becomes positively charged, and the material that gains electrons becomes negatively charged.

How is total resistance calculated in a series circuit?

RT = R1 + R2 + R3 + R4.

How is total resistance calculated in a parallel circuit?

1/RT = 1/R1 + 1/R2 + 1/R3.

How does voltage behave in a series circuit?

The voltage adds up to equal the total voltage.

How does current behave in a series circuit?

The current is the same throughout the circuit.

How does resistance behave in a series circuit?

Resistance adds up to equal the total resistance.

What happens when a negatively charged object touches a neutral object?

Electrons from the negatively charged object transfer to the neutral object, resulting in both objects having a negative charge.

What is charging by induction?

Bringing two objects close without touching, requiring grounding of the neutral object.

How do charges behave in insulators?

Charges cannot move through insulators.

What does the law of charges state?

Like charges repel, and unlike charges attract.

What is the purpose of the electrostatic series?

It is used to determine the final charge on objects when charging by friction.

What is required for charging by conduction (contact)?

When charging by conduction/contact, the two objects have different charges before contact, with one often being neutral.

What happens as charged and neutral objects are brought close during conduction?

The charged object induces a charge separation in the neutral object.

What happens when a negatively charged rod is brought near a neutral sphere?

The neutral sphere repels the negatively charged rod, creating a charge separation (induced charge separation).

What is the formula for calculating current?

I=V/R.

What is the current flowing through a toaster (120V outlet, 14Ω resistance)?

8.57A.

What is the resistance of a can opener (1.5A current, 120V outlet)?

80Ω.

What is current and how is it measured?

Current is the rate at which electrons flow past a point in a circuit, measured in amps (A).

What is potential difference and how is it measured?

Potential difference is a measure of the difference in electric potential energy between two points in a circuit, measured in volts (V).

What determines the amount of energy each bundle of electrons gives to a load?

The amount of work needed to move through a load is determined by the resistance of the load.

What is resistance?

Resistance is the ability of a material to oppose or impede the flow of electric current.

What is the purpose of grounding?

It prevents the build-up of static charge and allows for controlled discharge of electrons.

What is electrical current?

Moving electrons in a path called a circuit.

What are the four components of a circuit?

Load, Connectors, Control device, Power supply.

What is the function of a load in a circuit?

Converts electric potential energy into other forms (e.g., light, fan, motor).

What is the function of connectors in a circuit?

Connects all components and provides a pathway for electron flow (e.g., wires).

What is the function of a control device in a circuit?

Opens and closes the pathway, controlling electron flow (e.g., switches).

What is the function of a power supply in a circuit?

The source of electric potential energy (e.g., battery).

How do electrons behave in a closed circuit?

Electrons exit the negative end of the battery, give energy to the load, and return to the positive end.

What are the two types of power supplies?

Direct current (DC) and alternating current (AC).

What is the function of resistors in a circuit?

Resistors control the flow of electrical current in a circuit.

What device is used to measure resistance?

An ohmmeter.

Give examples of good conductors.

Silver, copper, and aluminum.

Give examples of good insulators.

Plastic, wool, and rubber.

How can you remove a static charge buildup?

Touching a metal object.

What does 'discharge' mean in the context of static electricity?

Returning to neutral.

What are sparks?

When electrons jump through the air from one object to another, which is uncontrolled.

What is voltage?

Electric potential energy that helps electrons move.

What is potential difference?

The difference in voltage between two points in a circuit.

How is potential difference measured?

Using a voltmeter connected in parallel to a load.

What is a key rule about electron energy usage in a circuit?

Electrons must use all their energy before returning to the battery.

How must a voltmeter be connected in a circuit?

Parallel.

How is current distributed in a series circuit?

All loads on the same path get the same current.

How is current distributed in a parallel circuit?

Current splits between different paths.

What are the rules for drawing simple circuits?

Ruler, 90-degree turns, and proper symbols.

How are loads connected in a series circuit?

Loads are connected one after another on the same path.

How are loads connected in a parallel circuit?

Loads are connected in parallel, providing multiple pathways for electrons.

What is an electroscope?

A metal ball connected to two thin metal strips that diverge when charged.

How does charge distribute on a metal sphere?

The charge spreads out all over the place because it's a conductor.

What is current (I)?

The rate at which electrons flow past a point in a circuit, measured in amperes (amps, A).

How is conventional current defined?

Conventional current shows current going the opposite way of electrons.

What happens to electrons when they pass through a load?

Electrons lose energy, which the load changes into another form.

How is current measured?

Using an ammeter connected in series with the load.

How does voltage behave in a parallel circuit?

Voltage is the same throughout.

How does current behave in a parallel circuit?

Current adds up to equal the total.

How is energy lost during energy conversion?

Energy is lost as heat when loads convert electric energy to other useful forms.

How efficient are electrical appliances?

Appliances use only a portion of the supplied electrical energy to do their job, losing the rest as heat.

How is efficiency calculated?

Efficiency = (useful energy output / total energy input) x 100.

What is the efficiency of a fluorescent light bulb (2000J input, 400J output)?

20%.

Relate the amount of kWh to expense.

The smaller the kWh the less expense it would be since it takes more power.

What is the charge of an object with an equal number of protons and electrons?

Neutral.

What is the charge of an object that has lost electrons?

Positive.

What is the charge of an object that has gained electrons?

Negative.

What are materials that allow electrons to flow through easily called?

Conductors.

What are materials that do not allow electrons to flow through easily called?

Insulators.

What happens to resistance as the temperature of a material increases?

Increase.

According to Ohm's Law, what is equal to potential difference divided by current?

Resistance.

What type of electricity is a buildup of charge in one area that does not move?

Static Electricity.

What are the three ways to build up static charge?

Friction, conduction, and induction.

In what type of circuit does the current remain the same throughout?

Series.

In what type of circuit does the current split between different paths?

Parallel.

What can prevent the buildup of static charge?

Grounding.

What device is used to measure potential difference?

Voltmeter.

In what type of circuit must an ammeter be connected?

Series.

In what form is energy often lost when it changes from one form to another?

Heat.

What is the term for how well an appliance uses the electrical energy it receives?

Efficiency.

Electrical current involves the movement of what particles?

Electrons.

What is the path called in which electrons move in electrical current?

Circuit.

What is the unit of measurement for resistance?

Ohm.

What is the unit of measurement for potential difference?

Volt.

What is the unit of measurement for current?

Ampere.

According to Ohm's Law, what happens to current as potential difference across a load increases?

Increases.

Do unlike charges attract or repel one another?

Attract.

Do like charges attract or repel one another?

Repel.

What are connectors in an electrical circuit often made of?

Wires.