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Charge, Q = 10C

Time, t = 5s

Charge flowing in one second = \(\frac{10}{5}\) = 2 C/s

• In B, the blue wire is broken. Hence circuit is incomplete and current does not flow. Therefore, bulb will not light up.
• In C, the red wire is broken. Hence circuit is incomplete and current does not flow. Therefore, bulb will not light up.
• In D, both wires are connected to the same terminal. Hence, there is no potential difference and current does not flow. Therefore, bulb will not light up.

A: Wire is broken at the negative terminal. Bulb will not glow as the circuit is incomplete. 

B: Wire is disconnected at the negative terminal. Bulb will not glow as the circuit is incomplete. 

C: The circuit is complete. Therefore, bulb will glow. 

D: Rubber is a bad conductor of electricity. Hence, it will not allow current to flow and the bulb will not glow.

(a) When the clamp is removed, water flows from higher level to lower level.

(b) Yes, the water stops flowing. This happens when the level of water becomes equal in both the bottles, i.e., there is no difference in the water levels.

(c) The difference in the water level has to be maintained till that time. The difference must never be zero.

A. insulators

Two terminal electric cell consists of

B. movable electric charge

The device which easily closes or opens an electric circuit is called as  switch.

A. protecting from shock

Plastic is bad conductor of electricity.

For carbon, resistance decreases with increase in temperature.

Hint: For semiconductors such as carbon and silicon, the resistance and resistivity decreases with the increase in temperature.

A. Area of cross-section

Ammeter consists of a wire of low resistance when connected in parallel, a large amount of current passes through it hence gets burnt i.e. short-circuited.

In series combination, resistance increases due to increase in  Length.

A. A parallel combination of two resistances and one in series

 Conductance is expressed in terms of mho.

Siemen (s) or mho (Ʊ). 

The reciprocal of resistance is called electrical conductance (G). G = 1/R 

The resistance (R) of a conductor is inversely proportional to its area of cross section (A). i.e., R ∝ 1/A

A current whose magnitude does not change with time is called steady current. 

A current whose magnitude changes with time is called varying current.

The resistance (R) of a conductor is directly proportional to its length (l) i. e., R ∝ l 

The resistance of a conductor is I ohm if one ampere of current flows through it when the potential difference across its ends is one volt.  

The direction of conventional current in an electric circuit tells the direction of flow of positive charges in that circuit. 

It is defined as the ratio of the potential difference (V) across the ends of the conductor to the electric current (I) through it. or R = V/ I. 

The net flow of electric charges in any direction inside the solid conductor is zero.

Ohm’s law states that the current (I) flowing through a conductor is directly proportional to the potential difference (V) applied across its ends, provided the temperature and other physical conditions remain constant”. i.e. I or V = IR. 

Free electrons in solid conductors/ positively and negatively charged ions in liquid conductors and / positive ions and electrons in gaseous conductors.  

Zero

The resistance of an ammeter should be very small and for an ideal ammeter, its value is zero.

B.  V = W / Q

D. not determine

A complete electric circuit is called as closed.

2 terminals an electric bulb consists of.

D. ammeter should be connected in series and voltmeter in parallel 

(i) By increasing resistance R the current through AB decreases, so potential gradient decreases. Hence a greater length of wire would be needed for balancing the same potential difference. So the null point would shift towards B.

(ii) By decreasing resistance S, the current through AB remains the same, potential gradient does not change. As K₂ is open so there is no effect of S on null point.

(i) By increasing resistance R, the current in main circuit decreases, so potential gradient decreases. Hence a greater length of wire would be needed for balancing the same potential difference. So, the null point would shift towards right (i.e., towards B)..

(ii) By decreasing resistance S, the terminal potential difference V = ε – Ir, 

where I = \(\frac{\epsilon}{(r\,+\,S)}\,V=\frac{\epsilon}{1+\frac{r}{s}}\) across cell decreases, so balance is obtained at small length i.e.,

point will be obtained at smaller length. So, the null point would shift towards left (i.e., towards A).

While drifting, the free electrons collide with the ions and atoms of the conductor i.e., motion of the electrons is opposed during the collisions, this is the basic cause of resistance in a conductor. 

The maximum current that can be drawn from a voltage supply is given by,

\(I_{max}=\frac{E}{r}\)Obviously, \(I_{max}\) will be large, if r is small.

If the circuit containing the H.T supply gets short circuited accidently, the current in the circuit will not exceed the safe limit, in case the internal resistance of H.T supply is very large.

Electrical resistivity of a material is defined as the resistance offered to current flow by a conductor of unit length having unit area of cross section.

Materials for which the current against voltage graph is a straight line through the origin, are said to obey Ohm’s law and their behaviour is said to be ohmic. Materials or devices that do not follow Ohm’s law are said to be non-ohmic.

The resistance of some conductors becomes nearly zero if their temperature is decreased up to a certain value close to 0 K. Such conductors are called superconductors.

Conductors which do not obey Ohm’s law are called non-ohmic conductors.

(i) To obey elders.

(ii) Using, I = V/R,

(a) 147 mA;

(b) 2.2 mA

(c) Wet skin with 147 mA

(iii) When the current flows, the result is fatal.

The expression for equivalent internal resistance of n cells each of internal resistance r connected in series.  

r_eq = n r 

1. The potential difference between the ends of the potentiometer wire or the emf of the cell connected in the main circuit may not be greater than the emf of the cells whose emf are to be compared.

2. The positive terminals of the cells and the battery used in the circuit might not be connected to the same end of the potentiometer wire.

 3. The rheostat might not be adjusted properly and kept in such a position that it offers minimum resistance to the circuit and allows maximum current through the wire.

If the emf of the cell is decreased, the potential gradient across the wire will decrease. Due to this the position of zero deflection will be obtained on the longer length. 

A mesh or loop is a closed path with in the network for the flow of electric current. 

Conservation of charge. 

At any junction in an electric network the sum of the currents entering the junction is equal to sum of the currents leaving the junction.