Electricity - Science Unit 9 S2A Stage 9

Flashcards on Electricity

Electric current is the flow of electric charge through a conductor.

What is electric current?

Voltage is the measure of the potential difference in charge between two points in a circuit.

Voltage is the one pushing for current to flow. Voltage is like the pressure or push behind the flow of current. It is also referred to as the potential difference.

What is voltage?

Resistance is how easy or difficult it is for electrons to move through a material. → It is the opposition of the flow of current through a material.

Resistance is a measure of how much a material opposes the flow of electric current going through it.

Resistance is measured in units called ohms. Ohms are represented by the Greek letter omega.

• Resistance SLOWS the flow of electrons, so it LOWERS CURRENT.

• The greater the resistance in a circuit, the smaller the current in the circuit.

What is resistance?

Longer = higher resistance

Shorter = lower resistance

Wider/Thicker = lower resistance

Narrower/Thinner = lower resistance

→ This is because when a material is thicker and shorter, there are less chances of the electrons of the current bumping into the atoms of the material, thus hindering the flow of current. So, the resistance would be lower, and the current would be higher.

Which factors affect resistance?

• Conductors have very low resistance so that current can flow easily through them.

• Insulators, such as most plastics, have very high resistance so that current cannot flow through them.

• Some conductors are designed to have a very high resistance. In some lamps, there is a wire called a filament, which has a high resistance. When current flows through the filament, thermal energy is transferred. There is so much thermal energy that the filament GLOWS and emits LIGHT.

• Resistors control the amount of current. It ensures that the devices work safely, and that there is no overheating or damage to appliances.

Examples of resistance:

Electrical circuits are closed loops or pathways through which current flows.

An electrical circuit is a basic circuit with atleast one power source, wires, a load and a switch (optional if the wires are connected to the power source and load already without the switch, closing the circuit permanently.)

What is an electrical circuit?

A series circuit is a circuit where in all components are connected end-to-end, forming a single pathway for current to flow.

A series circuit is an electrical circuit where all components are connected together by their terminals in a single pathway. In a series circuit, all components are connected end-to-end in a single path.

What is a series circuit?

• The same current flows through each component.

• If one component fails, the entire circuit stops working.

• A circuit switch will control the flow of electricity through all components.

• Current is the same in all parts of the circuit.
  → This is because the circuit has no branches and only has one path for the current to flow in.

• Total voltage is shared among all components.

• The voltage in a series circuit can be different across different components.

• The voltages across all the components in a series circuit add up to the voltage of the supply.

• Total resistance = sum of all resistances (R_total = R1 + R2 + …) OR R(total) = R(1) + R(2)

• More components increase total resistance.

• Adding more components decreases the total current.

• Adding more components decreases the individual voltage each component gets.

• As components are added, it becomes difficult for the power supply to push electrons around the circuit, so the resistance increases, thereby decreasing the current flow.

What are the characteristics of series circuits?

• It would increase the current in the circuit.

• It would increase the voltage across each component.

What would increasing the number of cells in the same series circuit do?

A parallel circuit is a circuit with branches where current can flow through more than one route.

• In a parallel circuit, components are connected across common points, creating multiple paths for electricity to flow.

• Each branch receives the same voltage.

• If one component fails, the other branches continue to function.

• A circuit switch will control the flow of electricity through all components.

What is a parallel circuit?

• Each branch receives the same voltage.

• If one component fails, the other branches continue to function.

• A circuit switch will control the flow of electricity through all components.

• The current is split between the branches of the circuit. The sum of the currents of all branches is equal to the total current that flows from the cell / battery. In other words, the total current through the whole circuit is the sum of the currents through the separate components.

• In a parallel circuit, the total current from the cell equals the sum of the currents in all the branches.

  In short:

  Current in = current split up + added back together

• The current in a parallel circuit is split between branches based on resistance.

• The voltage in all branches of a parallel circuit is the same. This is because current can flow in different paths, so each branch gets the full voltage of the supply.

• Adding more components in a parallel circuit, or adding more branches to a parallel circuit gives more paths for the current to flow through. The more paths there are for current to flow through, the easier it becomes for electrons to move swiftly through the circuit. (Resistance decreases) → Thus, the total current through the cell INCREASES.

• Adding more components to any one branch of a parallel circuit will decrease the current in that branch.

• Total resistance is worked out using the reciprocal of the resistances of each branch. If there are 3 branches to the circuit (R1 – R3), then 1 / Total Resistance = 1 / R1 + 1 / R2 + 1 / R3.

What are the characteristics of a parallel circuit?

• Symbols are used to represent actual electrical components and are two dimensional

• Lines are used to represent wires that connect all components of a circuit together

• Circuits are shown as a closed loop

• Circuits always are anticlockwise

Characteristics of circuit diagrams

• Increases the voltage across each branch

• Increases the current through the cell

• Increases the current through each branch

What would increasing the number of cells in the same parallel circuit do?

SERIES CIRCUIT:

Resistors in series increase resistance. In a series circuit, adding resistors will increase resistance.

The more resistors added, the harder it is for current to flow.

PARALLEL CIRCUIT:

Resistors in parallel decrease resistance. In a parallel circuit, adding resistors will decrease the resistance.

The more resistors added, the easier it is for current to flow through many pathways.

Adding Resistors/components in a Series Circuit VS Adding Resistors/components in a Parallel Circuit

Voltage = Current x Resistance

V = IR

V = Voltage, in volts

I = current, in amps

R = resistance, in ohms

State Ohm’s Law.

You use an ammeter to measure the current in a circuit. It has to be connected in SERIES with the measured appliance.

How do you measure the current in a circuit?

You can use a voltmeter to measure the voltage in a circuit. It has to be connected in PARALLEL to the measured appliance.

How do you measure the voltage in a circuit?

You can use a ohmmeter to measure the voltage in a circuit. It must be connected in PARALLEL to the measured component, and the circuit should be opened/powered off.

How do you measure the resistance in a circuit?

• Voltage is linked to the electrical energy in a circuit.

• Voltage is linked to the energy changed by components in a circuit.

• Voltage in SERIES CIRCUITS are distributed based on how much energy each components CHANGES. If it changes more energy, it gets more voltage.

• Energy is always constant, so the energy changed by components in a circuit must always add up to the same amount of total voltage in the power source.

More on voltage:

It will generally increase as a parallel circuit includes more pathways for the current to flow, thus decreasing total resistance and increasing the total current under the same voltage.

What will happen to the total current if you change from a series circuit to a parallel circuit?

A resistor is an electrical component designed to have a known resistance.

What is a resistor?

1. Christmas lights

2. Flashlight

3. Coffee Machines

4. Water heaters

5. Cooling compressor in fridges

6. Thermostat switch in fridges

What appliances use series circuits?

1. Household lights

2. Electric fans

3. Car Headlights

4. TVs

5. Washing machines

6. Refrigerators

What appliances use parallel circuits?

Resistance in a circuit is primarily affected by the material's type, its length, its cross-sectional area (thickness), and its temperature, with longer, thinner, hotter conductors made of less conductive materials having higher resistance, while thicker, cooler conductors of good conductive materials offer less opposition to current flow. 

1. Material type

2. Material length

3. Material thickness/cross-sectional area

4. Temperature

What factors affect resistance?

If the circuit switch is closed, electricity flows through all components.

What happens when you close the switch of an electrical circuit?

If the circuit switch is opened, electricity cannot flow through all components.

What happens when you open the switch of an electrical circuit?

• The amount of current in the circuit.

• The voltage of the cell/power source in the circuit.

• The amount of resistance in the circuit.

What are the factors affecting appliance/load performance?

A coffee maker operates using a series circuit, linking the power switch, heating element, and indicator light in a single pathway.

When the switch is on, the circuit closes, allowing electricity to flow. When the switch is off, the circuit opens, stopping the flow.

How does a series circuit in a coffee maker work?

• Series circuits provide one path for current, while parallel circuits provide multiple paths.

• Closed circuits allow for electricity to flow

• Opened circuits do not allow for electricity to flow

• Circuit diagrams help us visualize and understand electrical systems.

Summary of Circuits