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Science chapter 13 Flashcards

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1
Q

An electrical system comprises of

A

-connecting wires
-dry cell, one
-dry cells, two in
series
-switch (open)
-switch (closed)
-light bulb

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2
Q

The SI unit of current is the

A

ampere (A). One ampere of
current means that one unit charge flows in one second.

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2
Q

We measure current using an

A

ammeter, + to +, - to -

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3
Q

What is an electric current

A

An electric current is the rate of flow of electric charge.

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3
Q

How does conventional current flow

A

current flows
from the positive terminal of a battery to
the negative terminal.

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4
Q

How does the electron current flow

A

it flows from the negative to the
positive terminal.

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4
Q

An electric current can flow only
when there is a

A

potential difference

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4
Q

An ammeter must be connected in

A

series in a
circuit.

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5
Q
A
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6
Q

What is the potential difference between any two points

A

it is the amount of energy needed to move one unit of electric charge from one point to another

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6
Q
A
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7
Q

The SI unit of potential difference is

A

Volt (V)

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8
Q

The more energy needed to move a charge
between two points in a circuit, the greater the
potential difference between the two points.

A

the greater the
potential difference between the two points.

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9
Q

We measure potential difference using a

A

voltmeter

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10
Q

The voltmeter must be connected in

A

parallel

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11
Q

What is the resistance of a component is the ratio of
the potential difference across it to the current
flowing through it.

A

It is the ratio of
the potential difference across it to the current
flowing through it.

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11
Q

What is the SI unit of resistance

A

ohm (Ω).

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11
Q

The greater the ratio of V to I, the

A

greater the
resistance.

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12
Q

The resistance of an object depends on factors such as

A

the cross-sectional area, length and type of material the
object is made of.

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13
Q

What are fixed resistors

A

the
resistance of the circuit cannot be changed
unless the resistors themselves are changed.

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13
Q

the resistance of the circuit cannot be changed
unless

A

the resistors themselves are changed.

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14
Q

In a series circuit, the electrical components are joined one after another to form a single loop. Electric current passes through a single path in a series circuit.

A

one after another to form a single loop. Electric current passes through a single path in a series circuit.

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14
Q

A variable resistor or rheostat allows us to

A

adjust the resistance in a circuit.

15
Q

In a parallel circuit, the electric current is divided into

A

into branches. Electrical components (e.g. bulbs) are connected in each branch. Electric current passes through all branches of a parallel circuit.

15
Q

The higher the resistance, the

A

dimmer the bulb

16
Q

When the rheostat slider is on
the left, the

A

short
resistance wire offers
low resistance.(bulb is brighter)

17
Q

In a series circuit, the current at every point is …
the sum of the potential difference across
each component is equal to …
Vε = V1 + V2 + V3 + … + Vn

A

the same; , the potential
difference across the whole circuit.

18
Q

In a series circuit, the effective resistance R is the
R = R1 + R2 + . . . + R

A

sum of all the resistances.

19
Q

In a series circuit, the effective resistance is always

A

greater than the largest of the individual resistances.

20
Q

V = IR

A

V: voltage (V)

I: current (A)

R: resistance (Ω)

20
Q

What can an electric current cause when it is passed through certain liquids? What is the chemical effect used in?

A

-An electric current can cause a chemical
change when it is passed through certain
liquids.
-This chemical effect is used in electrolysis
and extraction of metals.

20
Q

For n resistors placed in parallel, the effective
resistance R is given by

A

1/r = 1/r 1 + 1/r2 + 1/r3 …
then aft that the ans
r/num
e.g. 1/3+1/3 = 2/3
resistance = 3/2

21
Q

the potential difference across each branch
is equal to

A

the potential difference across
the whole circuit.

21
Q

In a parallel circuit, the sum of individual currents in each of the
branches
Iε = I1 + I2 + I3 + … + In

A

is equal to the main current.

22
Q

What is electrolysis

A

Electricity can be used to break down
(decompose) compounds into its elements.
This process is called electrolysis.

22
Q

An electric current has an effect on … this effect can be seen when

A

magnets.

This effect can be seen when an electric
current flows near a compass.

22
Q

The magnetic effect can be increased by making
current flow in a coil of wire called a

A

solenoid.

23
Q

The power of a circuit component is

A

the
amount of electrical energy converted to other
forms of energy per unit time by the
component.

24
Q

The SI unit of power is

A

watt (W)

24
Q

What is electroplating

A

Many objects are coated with a metal by
immersing the object in a liquid and then passing
an electric current through the liquid.
This method of coating objects with metals is
called electroplating.

24
Q

1 kW = 1000 W

A
24
Q

The formula of energy =

A

energy = power X time

25
Q

Hazards of electricity

A

electrical fires, electric shocks and electrocution

26
Q

Safety features in the household electrical system

A

earth wire, fuse and circuit breaker

27
Q

The … wire
(blue) is at 0 V.

A

neutral

28
Q

The … wire (yellow
and green) is at 0 V. It
is connected to the
… or …

A

earth, ground or earth

29
Q

The … wire (brown) is
at a high voltage. In
Singapore, it is at … V.

A

live, 240

30
Q

which wire is connected to the fuse?

A

live wire

31
Q

Where is the neutral wire connected to?

A

The bottom left of the plug

32
Q

Where is the earth wire connected to?

A

The top middle part of the plug

33
Q

electrical systems can produce effects like

A

heating effect, magnetic effect and chemical effect

34
Q

What does a fuse do

A

The fuse makes use of the heating
effect of an electric current to switch
off a large current. A large current causes a short, thin wire in the fuse to heat up and melt.

34
Q

A … can also cut off an electric
current. However, unlike a fuse, it does not need
to be replaced.

A

circuit breaker

35
Q

A blown fuse should be …
after an electrical fault has been
rectified.

A

replaced

36
Q

Why does a circuit breaker not need to be replaced?

A

When a damaged appliance or the damaged part
of the circuit is fixed, the circuit can be switched
on again using the circuit breaker.

science (14 decks)

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