Electricity

Question 1

What is the value of mains voltage (in the UK)?

Answer 1

Mains voltage is 230V.

Question 2

Describe what would happen to a positive charge if it was placed in the field shown.

Answer 2

A positive charge would accelerate towards the negative plate.

Question 3

What is the name of this component?

Answer 3

Loudspeaker

Question 4

What is the name of this component?

Answer 4

npn transistor

Question 5

How could the air-conditioning circuit (shown) be changed so that it switches on at a different temperature?

Answer 5

To switch the circuit on at a different temperature, the variable resistor could be adjusted.

Question 6

Which quantity is represented by the symbol Q?

Answer 6

Q = charge

Question 7

What is the name of this component?

Answer 7

Motor

Question 8

What is the name of this component?

Answer 8

L.E.D. (light-emitting diode)

Question 9

What is the name of this component?

Answer 9

Capacitor

Question 10

What unit is energy measured in?

Answer 10

Energy is measured in joules (J).

Question 11

Round off this number to 3 significant figures.

1,526.33

Answer 11

1,526.33 rounded off to 3 significant figures is

1,530

(the ‘2’ has been rounded up to 3)

Question 12

How many pencils are there?

Answer 12

Question 13

What unit is voltage measured in?

Answer 13

Voltage is measured in volts (V).

Question 14

What does the prefix k stand for?

Answer 14

k stands for kilo

kilo = x 10³

Question 15

What unit is charge measured in?

Answer 15

Charge is measured in coulombs (C).

Question 16

What effect does an electric field have on a charge?

Answer 16

An electric field causes a charge to accelerate (due to applying an unbalanced force)

Question 17

What is the definition of the term power?

Answer 17

Power is defined as the amount of energy used per second.

Question 18

What is the definition of current?

Answer 18

Current is how much electrical charge flows (past a point) in one second.

Question 19

What unit is power measured in?

Answer 19

Power is measured in watts (W).

Question 20

Which quantity is represented by the symbol P, in the equation shown?

Answer 20

P = power

Question 21

Describe how to use an ammeter to measure the current in a component.

Answer 21

An ammeter must be connected in series with a component.

Question 22

Which quantity is represented by the symbol R?

Answer 22

R = resistance

Question 23

Round off this number to 3 significant figures.

6.22789

Answer 23

6.22789 rounded off to 3 significant figures is

6.23

Question 24

How could the resistance of a component be found from this graph?

Answer 24

The resistance could be found by

(a) calculating the gradient of the graph
(b) choosing a point on the graph and calculating voltage / current

Question 25

What is the name of this component?

Answer 25

**Fuse**

Question 26

What does **d.c.** stand for and what does it mean?

Answer 26

**d.c.** stands for **direct current**, which means the **electrons flow in one direction only** (negative to positive).

Question 27

What is the name of this component?

Answer 27

**Variable resistor**

Question 28

What is the name of this component?

Answer 28

**Resistor**

Question 29

What is the name of this component?

Answer 29

**Lamp**

Question 30

Round off this number to **3 significant figures**. ## Footnote 3.14159

Answer 30

3.14159 rounded off to 3 significant figures is **3.14**

Question 31

What does **a.c.** stand for, and what does it mean?

Answer 31

**a.c.** stands for **alternating current**, which means the **electrons change direction every fraction of a second**.

Question 32

How could the **air-conditioning** circuit (shown) be changed so that it performs the **opposite job**?

Answer 32

The circuit can be changed to perform the **opposite job** by **swapping the thermistor with the variable resistor**.

Question 33

What does the prefix **G** stand for?

Answer 33

**G** stands for **giga** **giga** = **x 10⁹**

Question 34

Will the **L.E.D.** in this circuit switch on? Explain your answer.

Answer 34

**No** - the L.E.D. will not switch on. The positive terminal of the L.E.D. is **not** connected to the positive terminal of the battery.

Question 35

Which quantity is represented by the symbol **V**, in the equation shown ?

Answer 35

**voltage** | (or **potential difference**)

Question 36

Round off this number to **3 significant figures**. ## Footnote 0.0025668

Answer 36

0.0025668 rounded off to 3 significant figures is **0.00257**

Question 37

What does the prefix **m** stand for?

Answer 37

**m** stands for **milli** **milli = x 10^-3**

Question 38

What is the name of this component?

Answer 38

**MOSFET (transistor)**

Question 39

What is the name of this component?

Answer 39

**Diode**

Question 40

What is the name of this component?

Answer 40

**L.D.R. (light-dependent resistor)**

Question 41

Which quantity is represented by the symbol **I**?

Answer 41

**I** = **current**

Question 42

What does the prefix **M** stand for?

Answer 42

**M** stands for **mega** **mega = x 10⁶**

Question 43

What **unit** is **time** measured in?

Answer 43

Time is measured in **seconds** (**s**).

Question 44

Describe how to use a **voltmeter** to **measure the voltage** across a component.

Answer 44

A **voltmeter** must be **connected in parallel** with a component.

Question 45

What does the prefix **µ** stand for?

Answer 45

**µ** stands for **micro** **micro = x 10^-6**

Question 46

Why does an **L.E.D.** always have a resistor connected in series with it?

Answer 46

An L.E.D. always has a resistor connected in series with it to **protect the L.E.D.** The resistor will **limit the current in the L.E.D.**

Question 47

Which quantity is represented by the symbol **t**?

Answer 47

**t** = **time**

Question 48

A hairdryer has an operating **current** of **6.5 amperes**. What **value of fuse** should be used in the plug of the hairdryer?

Answer 48

The **fuse rating** has to be **higher than the operating current**. If the current is 6.5A, a **13A fuse** should be used.

Question 49

What **unit** is **current** measured in?

Answer 49

Current is measured in **amperes** (**A**).

Question 50

In the diagram shown, what **type of charge** does the **particle** have? Explain your answer.

Answer 50

The particle has a **negative charge**. The particle is negative because it is **attracted** to the **positive plate**.

Question 51

Describe what would happen to a **negative** **charge** if it was placed in the field shown.

Answer 51

A **negative charge** would **accelerate** towards the **positive** plate.

Question 52

What does the prefix **n** stand for?

Answer 52

**n** stands for **nano** **nano = x 10^-9**

Question 53

What **unit** is **resistance** measured in?

Answer 53

Resistance is measured in **ohms**.

Question 54

What is the name of this component?

Answer 54

**Cell**

Question 55

What is the name of this component?

Answer 55

**Battery**

Question 56

The **voltage** of a supply is a measure of the ................... **given to the charges** in a circuit.

Answer 56

The **voltage** of a supply is a measure of the **ENERGY** **given to the charges** in a circuit.

Question 57

Will the **L.E.D.** in this circuit switch on? Explain your answer.

Answer 57

**Yes** - the L.E.D. will switch on. The positive terminal of the L.E.D. is connected to the positive terminal of the battery.

Question 58

What is the purpose of a **transistor**?

Answer 58

A **transistor** acts as an **electronic switch**. (it switches **on** above a certain voltage)

Question 59

How many types of electric charge are there, and what are their names?

Answer 59

There are **two types** of **electric charge** - **positive** and **negative**