Grade 9 Science Homework Practice: Electricity

Electricity Homework Practice

Grade 9 Science Electricity Homework Practice Advanced 10 Questions 13 Views

Classroom Worksheet

Grade 9 Science Homework Practice: Electricity

Electricity Homework Practice

Name____________________________

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Score______ / 10

Grade: Grade 9

Subject: Science

Topic: Electricity

Time: 20 Minutes

Difficulty: Advanced

Questions: 10

Instructions:
Answer all 10 questions neatly. Show your work for calculation questions. Use correct scientific units and explain your reasoning in complete sentences where needed.

Skills Practiced:

Electricity
Science
Critical Thinking
Problem Solving

1Question

State the difference between current and voltage.

2Question

Identify whether each material is a conductor or an insulator: copper, rubber, wood, aluminum.

3Question

A circuit has a voltage of 12 V and a resistance of 4 Ω. Calculate the current.

4Question

A device draws 2 A of current when connected to a 9 V battery. Calculate its resistance.

5Question

Explain what happens to the brightness of a bulb in a simple series circuit if a second identical bulb is added. Why does this happen?

6Question

A charge of 24 coulombs passes through a wire in 6 seconds. Calculate the current.

7Question

Two resistors, 3 Ω and 6 Ω, are connected in series. Calculate the total resistance and the current if the circuit is powered by a 9 V source.

8Question

Two resistors, 3 Ω and 6 Ω, are connected in parallel. Calculate the total resistance.

9Question

A circuit contains a 12 V battery and a 3 Ω resistor. Calculate the power used by the resistor.

10Question

A student wants to design a safe household circuit. Explain two reasons why parallel circuits are used in homes instead of series circuits.

Answer Key

#	Answer
1	Current is the flow of electric charge, measured in amperes (A). Voltage is the electrical potential difference that drives current, measured in volts (V).
2	Copper: conductor; Rubber: insulator; Wood: insulator (dry wood); Aluminum: conductor.
3	Using Ohm’s law, I = V/R = 12/4 = 3 A. The current is 3 amperes.
4	Using Ohm’s law, R = V/I = 9/2 = 4.5 Ω. The resistance is 4.5 ohms.
5	The bulbs become dimmer. Adding a second bulb in series increases the total resistance, which reduces the current through the circuit, so each bulb receives less electrical energy per second.
6	Current, I = Q/t = 24/6 = 4 A. The current is 4 amperes.
7	In series, total resistance = 3 + 6 = 9 Ω. Current = V/R = 9/9 = 1 A. The total resistance is 9 ohms and the current is 1 ampere.
8	For parallel resistors: 1/Rt = 1/3 + 1/6 = 2/6 + 1/6 = 3/6 = 1/2, so Rt = 2 Ω. The total resistance is 2 ohms.
9	First find the current: I = V/R = 12/3 = 4 A. Then power P = VI = 12 × 4 = 48 W. The power is 48 watts.
10	Parallel circuits are used because each appliance gets the full supply voltage, so devices work properly. Also, each appliance can be turned on or off independently, and if one appliance fails, the others can still operate.