A brass disc and a carbon disc of same radius are assembled alternatively to make a cylindrical conductor. The resistance of the cylinder is independent of the temperature. The ratio of thickness of the brass disc to that of the carbon disc is ______. α is temperature coefficient of resistance & Neglect linear expansion
Out of the following which is not a poor conductor ?
Under what condition current passing through the resistance R can be increased by short circuiting the battery of emf E2. The internal resistances of the two batteries are r1 and r2 respectively.
The current through the circuit before the battery of emf E2 is short circuited, is
After short circuiting the battery of emf E2, current through the resistance R would be
i2= E1/R+r1 ...(ii)
Since, from equation (i) and (ii), we get
∴ E1/R+r1 > E1+E2/R+r1+r2
This gives E1r2>E2(R+r1)
ABCD is a square where each side is a uniform wire of resistance 1Ω. A point E lies on CD such that if a uniform wire of resistance 1W is connected across AE and constant potential difference is applied across A and C then B and E are equipotential.
Wire of resistance =1Ω
Keeping in view that, ABCD is a square where each side is uniform wire of resistance 1Ω. If a uniform wire of resistance 1Ω is connected across AE and a potential difference is applied across A and C, the points B and E will be equipotential; a point E on CD is CE/ ED =√2/1
∴ CE:ED= √2:1
Two current elements P and Q have current voltage characteristics as shown below :
Which of the graphs given below represents current voltage characteristics when P and Q are in series.
A battery is of emf E is being charged from a charger such that positive terminal of the battery is connected to terminal A of charger and negative terminal of the battery is connected to terminal B of charger. The internal resistance of the battery is r.
Power of battery in resistor appears as
Which of the following quantities do not change when a resistor connected to a battery is heated due to the current?
A metallic conductor of irregular cross-section is as shown in the figure. A constant potential difference is applied across the ends (1) and (2). Then :
A current passes through a wire of nonuniform cross section. Which of the following quantities are independent of the cross-section?
Drift speed and current density are inversely proportional to the area of cross-section of a wire. Thus, they are dependent on the cross-section. The charge crossing in a given time interval is independent of the area of cross-section of the wire. Free electron density is the total number of free electrons per unit volume of the wire. The density of free electrons depends on the distribution of the free electrons throughout the volume of the wire. It does not depend on the cross-section of the wire.
A simple circuit contains an ideal battery and a resistance R. If a second resistor is placed in parallel with the first.
In the circuit shown E, F, G and H are cells of e.m.f. 2V, 1V, 3V and 1V respectively and their internal resistances are 2W, 1W, 3W and 1W respectively.
Consider the circuit shown in the figure
The equivalent resistance of a group of resistances is R. If another resistance is connected in parallel to the group, its new equivalent becomes R1 & if it is connected in series to the group, its new equivalent becomes R2 we have
The equivalent resistance of the group of resistances is R.
a resistance r(say) is connected in parallel to the group, its new equivalent resistance R1 is
a resistance r is connected in series to the group, its new equivalent resistance R2 is
The value of the resistance R in figure is adjusted such that power dissipated in the 2W resistor is maximum. Under this condition
Statement-1 : When two conducting wires of different resistivity having same cross section area are joined in series, the electric field in them would be equal when they carry current.
Statement-2 : When wires are in series they carry equal current.
Statement-1 : Potential difference across the terminals of a battery is always less than its emf.
Statement-2 : A battery always has some internal resistance.
Statement-1 : Knowing that rating is done at steady state of the filament, an electric bulb connected to a source having rated voltage consumes more than rated power just after it is switched on.
Statement-2 : When filament is at room temperature its resistance is less than its resistance when the bulb is fully illuminated
Statement-1 : When a battery is supplying power to a circuit, work done by electrostatic forces on electrolyte ions inside the battery is positive
Statement-2 : Electric field is directed from positive to negative electrode inside a battery
Statement-1 : Conductivity of a metallic conductor decreases with increase in temperature.
Statement-2 : On increasing temperature the number of free electrons in the metallic conductar decreases.
A current of 0.50 ampere is passing through a CuSO4 solution. How many Cu++ions will be deposited on cathode in 10 seconds ?
A copper wire of radius 0.1 mm and resistance 1 kW is connected across a power supply of 20 V.
(a) How many electrons are transferred per second between the supply and the wire at one end ?
(b) Write down the current density in the wire.
A wire has a length of 2.0 m and a resistance of 5.0 W. Find the electric field existing inside the wire if it carries a current of 10 A.
(a) A car has a fresh storage battery of emf 12 V and internal resistance 5.0 × 10-2W. If the starter draws a current of 90 A, what is the terminal voltage of the battery when the starter is on ?
(b) After long use, the internal resistance of the storage battery increases to 500 W. What maximum current can be drawn from the battery ? Assume the emf of the battery to remains unchanged.
(c) If the discharged battery is charged by an external emf source, is the terminal voltage of the battery during charging greater of less than its emf 12 V ?
Find the current through the 10 W resistor shown in figure.