Review of Electricity

Terms:

Ampere – The ampere is the standard unit of measure of electric current. It is sometimes written as amp.

Alternating current (AC) – An electric current that reverses direction on a periodic basis. It is widely used to transport power on power lines.

Direct current (DC) – A type of current that only flows in one direction (unlike AC which periodically reverses direction).

Electric current – Electric current is the flow of electric charge through a material. The standard unit for electric current is the ampere.

Ohm – The standard unit of measure for resistance.

Ohm’s law – A law of physics that describes the relationship between voltage, current, and resistance using the equation V = IR.

Resistor – A basic electronic component that prevents the flow of electric current.

Volt – The standard unit of measure for electric potential (voltage).

Watt – The standard unit of measure used for electric power.

Questions:

1. What is the unit of measurement of current?

1. Meter
2. Volt
3. Ohm
4. Ampere

Answer: d) Ampere

Explanation: The unit of measurement of current is Ampere.

2. Fill in the blanks: current-voltage relationship is given by the formula _____

Answer: V=IR

3. Ohm’s law is named after which scientist?

It is named after the scientist Georg Simon Ohm.

4. _____ volt of pressure is needed to push one amp of current through one ohm of resistance.

1. Zero
2. One
3. Two
4. Three

Answer: b) One

5. The SI unit of electrical resistance is the _____

1. Kelvin
2. Volt
3. Ohm
4. Ampere

Answer: c) Ohm

6. The unit of power is

1. Siemens
2. Volts
3. Watts
4. Kelvin

Answer: c) Watt

7. As the voltage across a resistor is increased, what happens to the resistance of the resistor?

It decreases

It remains constant

It increases

8. Which equation correctly links voltage V, current I and resistance R?

V = I x R

V = I ÷ R

V = R ÷ I

• Which statement applies to the following circuit when the switch is closed?

Circuit with a switch, resistor and ammeter in series.

1. The circuit will work
2. The circuit will not work because there is no source of energy
3. The circuit will not work because there is a short circuit

• What kind of electrical signal does this diagram show?

1. AC
2. DC
3. Neither

• Which of the following describes this circuit?

Circuit with a battery and lamp, plus two open switches connected in parallel.

1. Switches in series
2. Switches in parallel
3. Lamps in series

• What is the current in this circuit?

Circuit with a 6 V battery connected in series with a 12 ohm resistor.

1. [6 A]
2. [2 A]
3. [0.5 A]

• What is the resistance of the resistor in this circuit?

Circuit with a 6 V battery connected in series with a resistor and an ammeter, which reads 0.3 A.

1. [20 Ω]
2. [1.8 Ω]
3. [0.05 Ω]

• If the resistance in this circuit is halved, what will the current be?

Circuit with a 6 V battery connected in series with a resistor and an ammeter, which reads 0.3 A.

1. [0.3 A]
2. [0.6 A]
3. [0.15 A]

• The diagram shows part of a circuit. What is the resistance of the resistor shown?

A resistor labelled R in series with an ammeter reading 3 A. A voltmeter connected across the resistor reads 12 V.

1. [9 Ω]
2. [4 Ω]
3. [0.25 Ω]

1. The diagram shows part of a circuit. What is the reading shown on the ammeter?

A 30-ohm resistor in series with an ammeter. A voltmeter connected across the resistor reads 9 V.

1. [0.3 A]
2. [3.3 A]
3. [21 A]

1. The diagram shows part of a circuit. What is the reading displayed on the voltmeter?

An 18-ohm resistor in series with an ammeter reading 0.3 A. A voltmeter is connected across the resistor.

1. [60 V]
2. [17.7 V]
3. [5.4 V]

1. What kind of a circuit is this?

Circuit with a battery and three 500 ohm resistors in series.

1. Series
2. Parallel
3. Neither

• What is the total resistance of this circuit?

Circuit with a battery and three 500 ohm resistors in series.

1. [500Ω]
2. [1000Ω]
3. [1500Ω] If the supply voltage is (12V), what is the current in this circuit?

Circuit with a battery and three 500 ohm resistors in series.

1. [0.005A]
2. [0.008A]
3. [0.012A]

• What kind of a circuit is this?

Circuit with a battery and three 500 ohm resistors in parallel.

1. Series
2. Parallel
3. Neither

What is the total resistance of this circuit?

Circuit with a battery and three 500 ohm resistors in parallel.

1. [1500Ω]
2. [500Ω]
3. [167Ω]

• If the current in each branch is (20mA), what is the supply voltage in this circuit?

Circuit with a battery and three 500 ohm resistors in parallel.

1. [3.3V]
2. [10V]
3. [30V]

• What is the resistance between (X) and (Y)?

       3 parallel resistors and 3 resistors in series between X and Y

1. [ 62.5 ohm]
2. [ 48.62 ohm]
3. [ 16.6 ohm]

• What is the relationship between power (P), energy (E) and time (t)?

            ……………………………………………………..

• A hair dryer has a power rating of 920W. It is operated from the mains supply. (You should know that the mains supply is 230V). Work out the answers to the following questions.

Calculate how much energy is transferred when the hair dryer is used for 2 minutes.

• How much will be the cost of consumption of energy if the cost of electricity is 5 baht per unit?

……………………………………………………………………..

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References:

https://byjus.com/physics/ohms-questions/

https://www.bbc.co.uk/bitesize/guides/zsgtw6f/test

https://www.ducksters.com/science/physics/electricity_glossary_and_terms.php