The resistance of an ammeter should be low. An ammeter has to be connected in series with the circuit to measure current. In case, its resistance is not very low, its inclusion in the circuit will reduce the current to be measured. In fact, an ideal ammeter is one which has zero resistance.

Electrical power determines the rate at which the energy is delivered by a current

Following are the advantages of connecting electrical devices in parallel with the battery:
(i) Parallel circuits divides the current among the electrical devices, so that they can have necessary amount of current to operate properly.
(ii) If one of the devices in a parallel combination fuses or fails, then the other devices keep working without being affected.

The resistance of a conductor depends on following factors:
(i) Length of the conductor.
(ii) Area of cross-section of the conductor.
(iii) Nature of material of the conductor.

The potential difference between two points is said to be 1 V if 1 J of work is done in moving 1 Coulomb of electric charge from one point to other point.

The SI unit of electric current is ampere (A).
The current flowing through a conductor is said to be 1A, if a charge of 1coulomb (C) flows through it in 1second (s)
or \(1 A=\frac{1 C}{1 s}\)

The flow of electric charge is known as electric current. Electric current is carried by moving electrons through a conductor. Electric current flows in opposite direction to the movement of electrons.

(a) Since two \(8\Omega \) resistors are in parallel, their effective resistance (\({ R }_{ P }\)) is given by,
\(\frac { 1 }{ { R }_{ P } } =\frac { 1 }{ 8 } +\frac { 1 }{ 8 } +\frac { 1 }{ 4 } \) or \({ R }_{ P }=4\Omega \)
(b) Total resistance in the circuit
\(R=4\Omega +{ R }_{ P }=4\Omega +4\Omega =84\Omega \)
Current through the electric circuit
\(I=\frac { V }{ R } =\frac { 8V }{ 8\Omega } =1A\)
(c) The potential difference \(4\Omega \) resistor V
 I \(=IR=1\times 4=4V\) 
(d) Power dissipated in \(​​​​4\Omega \) resistor P=\({ (I) }^{ 2 }\)
\(R={ (1) }^{ 2 }(4)=4W\)
(e) There is no difference in the readings of ammeters \({ A }_{ 1 }\) and  \({ A }_{ 2 }\) as same current flows through all elements in a series circuit.

A number of resistors are said to be connected in parallel if one end of each is connected to one point and the other end is connected to another point so that the potantial difference across each resistor is the same and is equal to the applied potential difference between the two points. If we connect a voltmeter first across R₁, then across R₂ ad lastly across R₃, it will show same voltage.

A number of resistors are said to be connected in series, if these are joined end to end and the same, current flows through each one of them when a potential difference is applied across the combination. If we connect ammeter first between the point A and R₁, then between R1 and R₂:R₂ and R₃ and lastly between R₃ and the point B; it is same as current.

At constant temperature, the current flowing through a conductor is directly proportional to the potential difference across its ends.
Onh's law does not hold good under all conditions as it is not a fundamental law of nature like Newton's laws. It is obeyed by metallic conductors only when physical condition like temperature etc., are kept unchanged. It is not obeyed by a lamp filament.