Grade 9 Science - Voltage and Current in Circuits

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Questions and Answers

In a series circuit, how is the total voltage calculated?

It is the sum of the voltages across each load. (correct)

It is the average of all voltages.

It is the minimum voltage among the loads.

It is the product of the voltages.

In a parallel circuit, the voltage across each load is different.

False (B)

What happens to the current in a parallel circuit as more devices are added?

The total current increases.

In series circuits, increasing the voltage will cause the bulbs to burn __________.

brighter Signup and view all the answers

Match the following circuit components with their functions:

Fuse = Breaks circuit when current is too high Circuit Breaker = Reusable device for overcurrent protection Resistor = Reduces current in the circuit Switch = Opens or closes a circuit Signup and view all the answers

What is a disadvantage of a series circuit?

If one component fails, the entire circuit stops working. (D) Signup and view all the answers

Adding more loads in a parallel circuit decreases the total current.

False (B) Signup and view all the answers

What issue can arise from increased current in a parallel circuit?

Wires can heat up and cause a fire. Signup and view all the answers

The equation for total current in a parallel circuit is __________.

Itotal = I1 + I2 + ... + In Signup and view all the answers

What is the function of a resistor in a circuit?

To reduce current in the circuit. (B) Signup and view all the answers

What happens to the total resistance in a series circuit as additional loads are added?

It increases. (D) Signup and view all the answers

In a parallel circuit, a break in one pathway affects the other pathways.

False (B) Signup and view all the answers

What is the primary characteristic of a series circuit?

One path for electron flow. Signup and view all the answers

In a parallel circuit, total resistance ______ as loads are added.

decreases Signup and view all the answers

Match the following circuit types with their characteristics:

Series Circuit = Current is the same throughout Parallel Circuit = A break in one path does not affect others Signup and view all the answers

What remains the same throughout a series circuit?

Current (C) Signup and view all the answers

What is the effect of adding an extra lane in a parallel circuit during rush hour?

The overall traffic flow improves. Signup and view all the answers

Fuses are typically wired in parallel to control the entire circuit.

False (B) Signup and view all the answers

The ______ provides the energy/force needed to supply all of the loads in a series circuit.

source of electric potential Signup and view all the answers

Describe the effect of adding more loads in a series circuit.

Total resistance increases and affects current flow. Signup and view all the answers

Study Notes

Grade 9 Science, Academic - Lesson 11.2 - Voltage and Current in Series and Parallel Circuits

Learning Goals: Understand how electrical circuits are designed using series and parallel configurations.
Success Criteria:
- Explain the difference between series and parallel circuits.
- Use circuit symbols to draw circuit diagrams.
- Explain how voltage (V), current (I), and resistance (R) are affected by the number of loads in a circuit.
Recap: Review of potential difference, current, and resistance.
Note Format: First series circuits, then parallel, to aid comparing/contrasting.
Series Circuits:
- One path for electron flow.
- If one part of the circuit is open, electron flow stops.
- Total resistance increases as loads are added (equivalent to adding more hurdles).
Parallel Circuits:
- Electrons can flow through multiple paths.
- A break in one path doesn't affect the others.
- Total resistance decreases as loads are added (like adding extra lanes to prevent traffic congestion).
Combination Circuits:
- Some circuits use both series and parallel components.
- Switches and fuses are often wired in series to control/protect the entire circuit.
Circuit Symbols:
- Diagrams showing fuses, circuit breakers, switches etc.
Practice Problems:
- Draw a circuit with a 2-cell battery, resistor and light bulb in series. Show correct polarity and electron flow.
- Draw a circuit with a 4.5 volt battery, two bulbs and a resistor in parallel, also including a fuse.
Series Circuit Current:
- Current is the same throughout the entire circuit.
- Total current = current through every part of the circuit.
Series Circuit Voltage:
- Voltage is the sum of the voltage across each load.
- Total voltage = the sum of the voltages across each component.
Parallel Circuit Current:
- Current is shared throughout the circuit and is equal to the sum of individual branch current.
- Total current = sum of the currents through all branches.
Parallel Circuit Voltage:
- Voltage is the same across each branch. All components use the same total supplied voltage.
Voltage and Current Relationships
Series Circuits: Disadvantages—If one component fails, the entire circuit is interrupted.
Parallel Circuits: Disadvantages—Adding more loads increases the current, risking overheating wires and causing a fire.
Safety devices (fuses/circuit breakers) are used to prevent these problems in home circuits. Their purpose is to interrupt the circuit if a high current is detected.
Practice: Circuit Analysis: Solve problems involving missing values in series or parallel circuits.

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Description

Explore the concepts of voltage and current in both series and parallel circuits in this Grade 9 science lesson. Understand how these configurations impact resistance and the flow of electricity. Use circuit symbols to visualize and differentiate between the two types of circuits.