Electricity 7&8 Flashcards
(188 cards)
1
Q
Dry cell eg
A
Voltaic cell , Daniel cell
2
Q
SI unit of electrical resistance
A
Ohm
3
Q
What is ammeter
A
An instrument used to measure current in amperes
4
Q
From where does current actually move in an electric cell
A
From negative to positive
5
Q
What is voltage
A
Difference in electrical potential energy,per unit of charge,btw two points.
6
Q
Device used to identify charge of the object
A
Electroscope eg gold least electroscope
7
Q
BOT -
A
1kWh
8
Q
Secondary cells are also called
A
Storage cells or accumulators
9
Q
What is galvanometer
A
Used to measure small electric current.
10
Q
Microwave electrical energy
A
1500W
11
Q
Eg of secondary cells
A
Lead accumulators.
12
Q
What do you mean by a 9 volt battery
A
It means that there is a potential difference of 9 volt between the 2 terminals which charges to move with a specific energy of 9 joules.
13
Q
Colour of neutral wire
A
Black or yellow or blue
14
Q
Diff btw parallel and series circuit
A
Parallel- same voltage
Series- share volta
15
Q
What is fuse
A
Is a wire made of tin and lead with a porcelain holder
16
Q
Colour of earth wire
A
Green
17
Q
Dry cell example
A
Modified Leclanche cell was discovered by Georges Leclanche
18
Q
1 kWh =
A
1000Wh
=3.6 x 10 raised to 6 joules in one hour
19
Q
1 coulomb is equal to the
A
Charge of many electrons( negative energy)that is 6.25 x 10 raised to 18
20
Q
Electric iron
A
1000W
21
Q
Induction
A
Charging the body by bringing a charged object closely to it
22
Q
Explain the working of secondary cell
A
There are six cells in one secondary cells. Each cell has one negative and one positive terminal . The negative cell is lead while the positive terminal is lead oxide . Each cell has a strength of 2 volts. The secondary cell contains Sulphuric acid. The vessel is made of hard rubber,glass or celluloid.
23
Q
SI unit of charge
A
Coulomb
24
Q
Electrical resistance is directly proportional to the
A
Temperature
25
How can you measure the intensity of electric current called ampere
If a charge of Q coulombs flow through a conductor in t time then intensity of electric current measured in amperes represented by I isQ/T . 1 ampere is 1 coulomb of charge flowing at a certain point at 1 second .
26
BOT full form
Board Of Trade unit
27
If there is more voltage
More current would flow
28
Colour of live wire
Red
29
What do you mean by anode and cathode
Anode is the metal to be deposited and is attached to the positive terminal. Cathode is the metal on which it has to be deposited .
30
SI unit of electric current
Ampere(I)
31
Explain process of electroplating
The copper sulphate sol, when electricity passes through it splits into cu2 + and so2-.cu2+ is attracted towards the cathode attached to the negative cell . Where electrons are given out by the electric cell.The cu2+ molecules absorb the electrons given out by the cell. They become stable molecules. After that ,the cu in the anode donates electrons to the positive terminal to create a stable ion called cu2+ Which is then attracted towards the cathode and takes electrons from the negative terminal to form a stable ion called cu. thus during this process the cu (copper)gets deposited on the cathode and the content of the anode gets eroded
32
Bulbs in a house are connected in ............connection
Parallel
33
Voltage main function
To push electrons in a circuit
34
Electrical energy used by air conditioner
2000 to 3000 W
35
Electrolyte used in simple voltaic cell
Sulphuric acid
36
A charged body creates an
Electric field around it
37
What is the relationship between an electric field and an magnetic field
A moving electric field creates a magnetic field and vice versa
38
According to the relationship between electric and magnetic fields what happens when a charged body moves
A charged body always has an electric field around it and as it moves a magnetic field is also created
39
In a proton the electric field radically points
Outwards
40
In an electron the electric field radically points
Inwards
41
Magnetic effect of electric current first discovered by
Hans Christian oersted
42
Electrical power is
Electrical energy / time
43
Instrument that measures electrical power in watts
Wattmeter
44
Ohms law
Voltage=rate of flow of current x resistance
| P= I x V
45
Joules law of heating
Heat energy liberated in a circuit is
| H = I*2 . R . T(time for which current is flowing)
46
1 Kwh = how many joules
3.6 x 10*6
47
All ionic compounds are
strong electrolytes, because they mostly break up into ions as they dissolve in water.
48
Why do ionic compounds dissociate in water
if the energy given off when the ions interact with water molecules compensates for the energy needed to break the ionic bonds in the solid and the energy required to separate the water molecules so that the ions can be inserted into solution.
49
Resistance of a resistor increases with its
First , Resistivity of that substance
| And also length increases-more distance the electrons have to bump
50
Resistance of a resistor is inversely proportional to
Area-as area increases the no of electrons flowing at a point through the resistor increases
51
Resistance offered by a resistor formula
R = p x length/ area (p - resistivity)
52
A example of a rechargeable battery
Ni - fe accumulator
53
1 horse power (hp) = ? Watts
746 watts
54
A charged body creates an
Electric field around it
55
What is the relationship between an electric field and an magnetic field
A moving electric field creates a magnetic field and vice versa
56
Magnetic effect of electric current first discovered by
Hans Christian oersted
57
Electrical power is
Electrical energy / time
58
Instrument that measures electrical power in watts
Wattmeter
59
Ohms law
Voltage=rate of flow of current x resistance
| P= I x V
60
Joules law of heating
Heat energy liberated in a circuit is
| H = I*2 . R . time for which current is flowing
61
1 Kwh = how many joules
3.6 x 10*6
62
Why do ionic compounds dissociate in water
if the energy given off when the ions interact with water molecules compensates for the energy needed to break the ionic bonds in the solid and the energy required to separate the water molecules so that the ions can be inserted into solution.
63
Diamagnetic objects ?
materials that are not affected by a magnetic field.
64
Paramagnetic objects
materials like aluminum or platinum which become magnetized in a magnetic field but their magnetism disappears when the field is removed.
65
Ferromagnetic objects
materials (such as iron and nickel) that can retain their magnetic properties when the magnetic field is removed.
66
Charge is a
Scalar quantity
67
Charge cannot exist without
Mass
68
Quantisation of charge
It means charge cannot have any arbitrary value but is defined as a integral multiple of the basic unit such as electron
69
Charge of one electron
1.6 x 10 raised to -19 C
70
Charge of an object (q) is
ne
e - charge of proton
n - any integer
71
Quantisation of charge was first suggested by
Michael faraday
72
Quantisation of charge experimentally demonstrated by
Millikan in 1912
73
Conservation of charge
Charge cannot be destroyed nor created
74
Charge is invariant
It means charge of an object always remains same , even if it is accelerated and until charge is removed from it.
75
3 methods of charging
Conduction
Friction
Induction
76
Which type of charging is most preferred
Induction because a charged body can be used to charge Maza y other objects without losing its charge
77
Dielectric constant also called
Relative permittivity
78
Dielectric constant denoted by
K
79
Coulomb's constant
K = 9 x 10 raised to 9 N m sq. C raised to -2
80
Principle of superposition (electricity)
It states that when a number of charges are interacting with each other , the total force on a given charge is vector sum of forces exerted on it by all other charges
81
Linear charge density
Charge per unit length
82
Linear charge density is represented by
Lambda
83
Surface charge density
Charge per unit area
84
Electric field ?
A region surrounding a charge in which its electrical effects are perceptible.
85
In an electric field , crowded lines represent
A stronger field
86
Number of lines originating or terminating on a charge is proportional to its
Magnitude
87
If a body has a charge of q , then no electric field lines (electrical flux) it has is
q / E°
| E° - permittivity of free space
88
E° is the value of
Permittivity of free space
89
E° value?
8.854 x 10*-12 C*2 N*-1 m*-1
90
Electric dipole
Pair of two equal and opposite charges separated by a small distance
91
Point charges
Point particles with electric charge
92
Inside a conductor electric field is
0
93
3 types of capacitors
Parallel plate capacitors
Cylindrical capacitor
Spherical capacitor
94
Capacitor function is to
Store Charge
95
A capacitor consists of
2 metal strips separated by an insulating material called dielectric
96
Every substance has a quality called
Dielectric constant - (K)
97
Capacitance of a capacitor tells us
How much charge it can store
98
Charge stored in the metal pieces are both
Equal and opposite
99
Capacitors are usually charged by a battery and the voltage between the metal pieces is equal to
The voltage of battery
100
Capacitance formula
C = Q/V
C - capacitance
Q - charge in one of the metal pieces
V - voltage between the metal pieces
101
When a dielectric is introduced between 2 metal pieces in a capacitor
The molecules in it gets polarised
102
Due to the polarisation of dielectric in a capacitor -
Voltage decreases.
C = Q/V
So capacitance increases
103
If a battery is connected when the dielectric is placed between the metal pieces of the capacitor
The polarisation of dielectric reduces voltage between the metal pieces
But it is the battery's responsibility to see that there is the same voltage in the entire circuit.
So it starts to accumulate more charge in both metal pieces to make the voltage stable,thus at this time, amount of charge in both metal pieces increases.
So according to the formula- C = Q/V - capacitance increases
104
Unit of capacitance
Farads (F)
105
How to calculate the change a dielectric will bring to the capacitance of capacitor
Every substance has something called dielectric constant (K).
So what you have to do is multiply the capacitance of the capacitor when it had no dielectric with the dielectric constant and that will be your new capacitance
106
pF -
Picofarad = 10*-12 farad
107
Capacitance is a
Scalar quantity
108
Insulators also called
Dielectrics
109
Electric constant
E° also termed as permittivity of free space.
| The symbol is read as epsilon naught
110
................ has lowest electrical permittivity
Vacuum
111
Dielectric constant (k) is
Electrical permittivity of that substance
Divided by
Electrical permittivity of vacuum
112
Every substance has a dielectric constant more than
1
113
Surface charge density represented by
Sigma
114
Strength of electric field
2 x Coulomb's constant x pi x surface density
115
What is electrical potential energy
If a charge Q moves with a voltage V then the change in potential energy of that charge is Q times V .
116
Potential energy stored in a capacitor ?
1/2 x Q(charge) x voltage
117
In any circuit connection if you add the voltages of each of the capacitors it will be equal to
The voltage of the battery
118
In a series connection capacitance is added by the formula
1/C = 1/C1 + 1/C2 + 1/C3 + ...........
119
In a parallel connection capacitance is added by the formula
C = C1 + C2
120
When two capacitors with different potentials are connected to each other then
Charge moves from the higher potential to the lower potential until the potential becomes equal. This equal potential is called common potential
121
Common potential of two capacitors
Total charge / total capacity
122
In a series connection ............ is same
In parallel connection ............ is same
( for capacitors )
Charge, voltage
123
Capacitance of a spherical conductor of radius R
4 x pie x permittivity of free space x R
124
Symbol for capacitor of variable capacitor has
an arrow
125
Electric flux represented by the Greek symbol
Phi
126
Electrical flux can be found by
Multiplying strength of the electric field E with area A of a surface perpendicular to the field
127
To formulas for electrical flux
```
Flux = electrical field x area = E x A
Flux = Q / E°
```
Q- charge enclosed
So flux = EA = Q / E°
128
Capacitance directly proportional to
Area
129
Maxwells equations contain how many equations
4
130
Maxwells equation?
Gauss' law
Gauss' law for magnetism
Ampere's law
Faraday's law
131
Gauss' law for magnetism
This law states that magnetic monopoles do not exist
| Every magnet is a dipole
132
Faraday's law states that
Any change to the magnetic environment of a coil of wire , would cause a voltage to be induced on the coil
133
Ampere' law states that
the magnetic field created by an electric current is proportional to the size of that electric current, with a constant of proportionality equal to the permeability of free space. .
134
An infinitely uniformly charged plane produces a
Constant electric field
135
Magnetic constant (mue 0)
4π × 10*−7 N/A2
136
Electric charge is a
Fundamental property
137
The discovery that amber rubbed by wool or silk attracted light objects was done by
Thales of Greece in 600 BC
138
Name electricity coined from the
Greek word - elektron meaning amber.
139
Property which differentiates the 2 kinds of charge
Polarisation of charge
140
Names were given to the 2 kinds of charge by
Benjamin Franklin
141
Who first observed that compass needle was deflected by a wire carrying electricity
Oersted , and supported by Michael faraday and Ampere.
142
Who proposed the theory which unified electric current and magnetism
Maxwell and Lorentz
143
An application which is connected in a circuit
Load (L)
144
Deflection of the needle on galvanometer shows
Presence of current and direction of deflection indicates direction of current
145
Ammeter is joined in
Series connection
146
An ammeter has a
Low resistance
147
In a series circuit, the current through each of the components is the same, and the voltage across the circuit is the sum of the voltages across each component. In a parallel circuit, the voltage across each of the components is the same, and the total current is the sum of the currents through each component.
Read
148
Resistance wires usually made of a compound called
Manganin
149
Rheostat
A device used to adjust the magnitude of current in a circuit by changing the length of resistance wire.
150
Symbol used for variable resistance
Rh
151
Voltmeter has high
Electrical resistance so that it does not draw out much current from the circuit
152
Manganin composition
84% copper , 12% manganese , 4% nickel
153
Lead accumulators also called
Acid accumulators
154
Ni-Fe accumulators also called
Alkali accumulators
155
Alternating current ?
A current whose both magnitude and direction change with time. The current repeats it's value after a fixed time
156
Voltage of current reaching in homes of India
230 Volts
157
In an electric cell the positive electrode is called
Cathode
158
Potential is a
Scalar quantity
159
Potential SI unit is
Volt
160
1 horsepower = how many watts
746
161
Resistors in the higher range is usually made of
Carbon
162
How quickly an electron can flow through a conductor
Electron mobility
163
Drift velocity
Average speed that a particle like an electron attains in a material due to an electric field
164
Drift velocity =
Electron mobility x strength of electric field
165
1 kWh is equal to
3.6 x 10 raised to 6 joules
166
Internal resistance of a cell represented by a
r
167
Electromotive force represented by
A laterally inverted 3
168
Kirchhoff's first law also called
Kirchhoff's junction law or Kirchhoff's current law
169
Kirchhoff's first law states that
total current entering a junction is equal to the total current leaving the junction. OR The algebraic sum of currents at a junction is zero.
170
Kirchhoff's second law also called
Kirchhoff's loop law or kirchhoff's voltage law
171
Meter bridge is a device used for
Measuring unknown resistance
172
On rubbing substances with each other , those substances which are likely to get a positive charge
Fur , wool
Glass
Hair
Nylon or acetate
173
On rubbing substances with each other , those substances which are likely to get a negative charge
Silk , ebonite , amber , rubber , plastic
174
Eg of semiconductors
Silicon , Germanium
175
Non electrolyte
A solution of a chemical compound which do not conduct electric current and hence do not undergo any chemical change
176
Eg of non electrolytes
Petrol , kerosene oil , diesel , vegetable oil , chloroform , carbon tetrachloride , alcohol , ether , benzene , distilled water
177
For making metals shiny it is usually electroplated with
Nickel and chromium
178
Coulomb was named after the French physicist
Charles Augustin de Coulomb
179
Triboelectric effect
a type of contact electrification on which certain materials become electrically charged after they come into frictional contact with a different material. Rubbing glass with fur, or a plastic comb through the hair, can build up triboelectricity.
180
Coulomb’s constant
8.987551
181
Electrostatic equilibrium definition
It is the position where the resultant force on a charged particle becomes 0.
182
Electric charge definition (IJSO book)
It is the intrinsic property of certain fundamental particles like electron, quarks etc due to which they PRODUCE magnetic and electric effects.
183
The charge of a macro body =
The excess or deficiency of electrons in the body.
184
An algebraic expression becomes a polynomial only when -
All the coefficients are real numbers.
| All the powers of the variables are positive integers.
185
A polynomial whose coefficients are all zeros :
Zero polynomial.
186
Degree of a zero polynomial is
Not defined.
187
The real number “c” is a root of f(x) only if
f(c) = 0
188
Proof of remainder theorem
p(x) = q(x) (x-a) + r
Let x = a
p(a) = q(a) x 0 + r
p(a) = r
