Adeline S2 Science Unit8.1-8.4 revision

These flashcards cover essential concepts regarding electrical circuits, current, voltage, resistance, and their applications.

What condition allows a bulb to light up in a circuit?

The bulb lights when connected via wires to a cell, forming a complete path.

What is an electrical circuit?

A complete path through which electric charges flow.

What are the two types of circuits?

Closed circuits (complete) and open circuits (incomplete).

What is the role of a cell in a circuit?

It acts as a source of electrical energy.

What do electrical conductors do?

They allow electricity to flow through them.

Give an example of an electrical conductor.

Metals, pencil lead (graphite), vinegar.

What are electrical insulators?

Materials that do not conduct electricity.

Give an example of an electrical insulator.

Plastics, wood, distilled water.

What is the function of a switch in a circuit?

A switch is used to open or close a circuit.

What happens when a switch is closed?

Conducting parts touch, completing the circuit.

What happens when a switch is open?

Conducting parts do not touch, creating an incomplete circuit.

How is electric current defined?

The flow of electric charges around a closed circuit.

What is the direction of current flow in a circuit?

From the positive terminal to the negative terminal of a cell.

What device is used to measure current?

An ammeter.

What is the unit of current?

The ampere (A).

What can happen if an ammeter is connected in the reverse direction?

It may damage the ammeter.

What is the relationship between voltage and current in a circuit?

Higher voltage leads to a larger current.

What is the analogical component to a water pump in an electrical circuit?

The cell, which supplies energy for charge flow.

What devices work using the heating effect of current?

Electric kettle, iron, hairdryer.

What is an electromagnet?

A coil of wire that acts as a magnet when current flows through it.

What is the purpose of an electromagnetic door lock?

It uses an electromagnet to attract a metal plate, keeping the door locked.

What does voltage indicate in a circuit?

How much energy the cell supplies for electric charges to flow.

How is voltage measured?

Using a voltmeter.

What is the unit of voltage?

The volt (V).

What effect does increasing voltage have on current?

Increasing voltage increases current.

What is resistance in a circuit?

It measures how difficult it is for current to pass through a conductor.

What is the unit of resistance?

The ohm ($\Omega$).

What happens to current when resistance increases?

The current decreases.

What is a resistor?

A circuit component with a specific resistance value.

What factors affect resistance in a wire?

Length, thickness, and material of the wire.

How does thickness affect resistance?

A thin wire has higher resistance than a thick wire of the same length.

What type of resistors can have adjustable resistance?

Variable resistors or rheostats.

What is a rheostat used for?

To adjust the size of the current in a circuit.

Give an example of where rheostats are used in everyday life.

Volume controls on hi-fi systems.

What effect does current have when flowing through a conductor?

It produces thermal energy, causing the conductor to heat up.

How is the current affected by a higher resistance?

Higher resistance makes current flow more difficult, resulting in smaller current.

What happens to the voltage if one cell is connected in the opposite direction?

The total voltage is lower than the sum of individual voltages.

How does a circuit symbol for a voltmeter look?

It shows how a voltmeter is connected to measure voltage in a circuit.

What is the purpose of circuit symbols?

To represent different components in a circuit.

What is the water flow model used for?

To understand electric circuits by comparing them to water flow analogies.

What do connecting wires do in a circuit?

They provide a path for electric current from the power source to the appliance.

A circuit has two cells, one providing $3V$ and the other $1.5V$. If connected in series with opposing polarities, what is the resultant voltage?

The resultant voltage would be $|3V - 1.5V| = 1.5V$.

Why is distilled water considered an electrical insulator, while tap water can conduct electricity?

Distilled water lacks ions; tap water contains dissolved minerals and salts which provide ions for conduction.

If you double the length of a wire in a circuit, assuming all other factors remain constant, what generally happens to its resistance?

The resistance generally doubles.

An incandescent light bulb works on the heating effect of current. Why does it produce light instead of just heat?

The filament heats up to such a high temperature that it becomes incandescent, emitting light as well as heat.

What is the primary difference in circuit behavior between connecting an ammeter in series versus connecting a voltmeter in parallel?

An ammeter has very low resistance to measure current flow through a branch in series. A voltmeter has very high resistance to measure potential difference across a component in parallel without drawing significant current.

In a simple circuit with a cell, why does increasing the number of cells connected in series (correctly) increase the current?

Connecting cells in series increases the total voltage (electromotive force), which drives a larger current through the same resistance.

A broken connecting wire creates an open circuit. Why does this immediately stop the flow of current?

An open circuit means there is no complete path for the electric charges to flow, thus current cannot circulate.

If electrical charge flows from positive to negative terminal, what actually moves through the wire and in what direction?

Electrons (negative charges) actually move from the negative terminal to the positive terminal. Conventional current (positive to negative) is defined opposite to electron flow.

What analogical component in the water flow model represents a resistor's effect on current?

A narrow pipe or a constriction that impedes water flow, requiring more pressure (voltage) to maintain the same flow rate (current).

Why is it important for the conducting parts of a switch to fully touch when closed?

To ensure a complete, low-resistance path for current flow, preventing arcing or excessive heat generation at incomplete contacts.