Chap 7 Flashcards
What does energy mean
the ability to do work
S.I. unit for energy
S.I. unit for energy is joule (J)
Energy cannot be ________ nor __________ but it can exist in various forms
-created
-destroyed
Forms of energy:
-Sound energy
-kinetic energy
-electrical energy
-light energy
-chemical energy
-elastic potential energy
-gravitational potential energy
-nuclear energy
-heat energy
How is sound energy produced
produced by a vibrating object
how is kinetic energy produced
produced by a moving object
how is electrical energy produced
produced by the electric charges that flow throughout
how is gravitational potential energy produced
energy stored in an object due to its position
how is elastic potential energy produced
stored in an object due to its condition
how is light energy produced
produced by an object that emits light
how is nuclear energy produced
obtained from elements such as plutonium and uranium
nuclear energy is also known as
atomic energy
how is heat energy produced
stored in hot object
how is chemical energy produced
produced from energy stored in chemical substances
Sources of energy
-Sun
-geothermal (uses heat energy frm earths inner core)
-water
-biomass (plants/animals)
-fossil fuel
-radioactive substance
-wave
-wind
Electrostatic charges happens when
when 2 objects (insulator) or materials are rubbed tgt
Electrostatic charges happens as a result of:
the transfer of electric charges between our body and the object that has static electric charges
Electrostatic charges are the
static charges
Electric charges consist of
positive charges (proton)
negative charges (electron)
Electrostatic forces is the:
the attraction and repulsion between the electric charges
Only the ______ are transferred form one object to the other, whereas the _____ do not move
-electrons
-protons
The object that gains electrons will be
negatively charged
The object that loses electrons will be
positively charged
The object that has equal number of protons and electrons is known as
neutral
Same charges _____ each other
repel
Opposite charges _______ each other
attract
Whats an electroscope
- a device used to detect the existence of electric charges on an object
The further the divergence of the object the higher the:
quantity of electrostatic charges accumulated
Friction between clouds and air causes the clouds to be:
charged with electric charges
Lighting is a result of:
the force of attraction that exists between the positive charges on the ground and the negative charges in the clouds
Electric current can be defined as the:
rate of flow of electric charges through a conductor
Flow of electric current can be measured by using an
ammeter
S.I. unit for electric current is
ampere (A)
Voltage is
the potential difference between two points
Voltage can be measured in ___ n using:
measured in Volt (V) by using a voltmeter
Resistance meaning:
the ability of a conductor to limit or resist the flow of electric current
unit measuring for resistance
ohm (Ω)
what r the 3 electrical quantities that r related to one another in a circuit
-current
-voltage
-resistance
The changes in magnitude of the electrical quantities will:
have an effect in the magnitude of the other quantities
The amount of current flowing through the circuit _______ as the resistance _____
-decreases
-increases
relationship between current (I), voltage (V) and resistance (R) is known as
Ohm’s Law
Ohm’s law can be written as:
V = IR
Ohm’s Law states that:
the electric current that flows through a conductor is directly proportional to the voltage across two ends of the conductor, provided the temp and other physical situations r the same
State the formulas to calculate ohms law
V = I xR
I = V/R
R = V/I
Whats an electric circuit
a complete path which enables electric current to flow
A complete electric circuit is made up of various
electrical components
State the electrical components in an electric circuit
-switch
-dry cell
-voltmeter
-galvanometer
-ammeter
-bulb
-resistor
-fuse
-variable resistor
Series circuit is:
made up of electrical components that are connected one after another where the current flows through in a single path
Parallel circuit is:
separated into several diff paths of electrical circuit and each parallel path has electrical components
An electric circuit can be connected in:
series or parallel
for series circuit: Current that flows through each bulb is the
same
for series circuit: The voltage is the _____ of the voltages across each bulb
sum
for series circuit: Effective resistance is the _____ resistance across the components
total
State advantages of series circuit
-every component in the circuit receives same amount of current
-every component is controlled by the same switch
-increase in voltage supplies more electric current
state disadvantages of series circuit
- when one of the electrical appliances is damaged, other electrical appliances ceases to function
- adding more electrical appliances increases resistance n decreases the flow of the current
- each electrical appliance cannot be switched off individually
for parallel circuit : voltage that flows across each resistor is the ___ as the voltage that flows __________
-same
-across the dry cell
for parallel circuit: Current is actually the _____ of current that:
-total amount
-flows through each resistor
state advantages of parallel circuit
- every electrical appliance can be switched on or off separately
- the increase in the number of electrical appliances does not affect the function of the other appliances in the same circuit
state the disadvantages of parallel circuit
- the voltage for every electrical appliance cannot be adjusted bcuz the voltage is the same as the source of voltage
The electrical wiring system in our homes is connected in parallel to ensure
every light gets the same voltage frm its main power supply
Magnets exist naturally in the form of
lodestones
man made magnets r made frm materials such as
iron, steel , cobalt and nickel
properties of a magnet:
-attracts magnetic materials
-has poles (north pole n south pole)
-freely suspended magnet shows north – —south direction
-like poles repel, unlike poles attract
Characteristics of magnetic field lines
- the magnetic field lines never meet or cross
- the magnetic field lines begin from the north pole and end at the south pole
- the magnetic field lines are closer to one another where the magnetic field is stronger
Magnetic field is:
the area around magnets with magnetic force
Electromagnet is:
a type of magnet that has temporary magnetic effect when electric current flows through it
pattern of the magnetic field field depends on the :
shape of the conductor used
Magnetic field lines are ____ where the magnetic field is _____
-closer
-stronger
The strength of the magnetic field _______ as it moves away from the _________
-reduces
-centre of the conductor
The pattern of the magnetic field produced is _________ by the the direction of the current that flows through the conductor
-not affected
the direction of the magnetic field is determined by the:
direction of the electric current
what determines the direction of the magnetic field of the current flow in a straight wire
-the right hand grip rule
Solenoid polarity can be determined by
observing the direction of the current flow
