Assuming that the colour code for the carbon resistors gives their accurate values, the colour code for the carbon resistor, used as R3, would be:
A potentiometer wire of length L and a resistance r is connected in series with a battery of e.m.f. E0 and resistance r1. An unknown e.m.f. E is balanced at a length l of the potentiometer wire. The e.m.f. E will be given by
PARAGRAPH 2In a thin rectangular metallic strip a constant current I flows along the positive x–direction, as shown in the figure. The length, width and thickness of the strip are ℓ, w and d, respectively.
A uniform magnetic field is applied on the strip along the positive y–direction. Due to this, the charge carriers experience a net deflection along the z–direction. This results in accumulation of charge carriers on the surface PQRS and appearance of equal and opposite charges on the face opposite to PQRS. A potential difference along the z–direction is thus developed. Charge accumulation continues until the magnetic force is balanced by the electric force. The current is assumed to be uniformly distributed on the cross section of the strip and carried by electrons.
Consider two different metallic strips (1 and 2) of the same material. Their lengths are the same, widths are w1 and w2 and thicknesses are d1 and d2, respectively. Two points K and M are symmetrically located on the opposite faces parallel to the x–y plane (see figure). V1 and V2 are the potential differences between K and M in strips 1 and 2, respectively. Then, for a given current I flowing through them in a given magnetic field strength B, the correct statement(s) is (are)
Reason: Rate of flow of electron's in one direction is equal to the rate of flow of protons in the opposite direction.
The supply voltage to a room is 120 V. The resistance of the lead wires is 6Ω. A 60 W bulb is already switched on. What is the decrease of voltage across the bulb, when a 240 W heater is switched on in parallel to the bulb?
A wire of resistance 4Ω is stretched to twice its original length. The resistance of stretched wire would be:
The internal resistance of a 2.1 V cell which gives a current of 0.2 A through a resistance of 10Ω is:
The resistances of the four arms P, Q, R and S in a Wheatstone’s bridge are 10 ohm, 30 ohm, 30 ohm and 90 ohm, respectively. The e.m.f. and internal resistance of the cell are 7 Volt and 5 ohm respectively. If the galvanometer resistance is 50 ohm, the current drawn from the cell will be:
The current in the circuit is
where the ratio (a/b) is 700°C. If the cold junction is kept at 0°C, then the neutral temperature is
Reason A thermocouple may be used as a radiation detector.
In the circuit shown the cells A and B have negligible resistances. For VA= 12V, R1= 500 and R = 100 the galvanometer (G) shows no deflection. The value of VB is:
A meter bridge is set − up as shown, to determine an unknown resistance ‘X’ using a standard 10 ohm resistor. The galvanometer shows null point when tapping − key is at 52 cm. mark. The end − corrections are 1 cm and 2 cm respectively for the ends A and B. The determined value of ‘X’ is
Reason: In the absence of electric field electrons move randomly in all directions.
Reason : The temperature coefficient of resistance for insulator is also positive.
Two batteries of different emf and different internal resistances are connected as shown. The voltage across AB in volts is
Incandescent bulbs are designed by keeping in mind that the resistance of their filament increases with the increase in temperature. If at room temperature, 100W, 60W and 40W bulbs have filament resistances R100, R60, and R40, respectively, the relation between these resistances is
To verify Ohm’s law, a student is provided with a test resistors RT, a small resistance R2, two identical galvanometers G1 and G2 and a variable voltage source V. The correct circuit to carry out the experiment is
When two identical batteries of internal resistance each are connected in series across a resistors R, the rate of heat produced in R if J1. When the same batteries are connected in parallel across R, the rate is J2. If J1 = 2.25 J2 then the value of R in is
R1 = 1Ω and C1 = 2μF
R2 = 2Ω and C2 = 4μF
The respective time constants (in μs) for the circuits I, II, III are
Choose the correct option out the following:
(A) P and Q
(B) Q and R
(C) P and R
(D) any two points
(A) B and C
(B) C and D
(C) A and D
(D) B' and C'
(a) Are there positive and negative terminals on the galvanometer?
(b) Copy the figure in your answer book and show the battery and the galvanometer (with jockey) connected at appropriate points.
(c) After appropriate connections are made, it is found that no deflection takes place in the galvanometer when the sliding jockey touches the wire at a distance of 60 cm from A. Obtain the value of the resistance X.
The effective resistance between the points P and Q of the electrical circuit shown in the figure is
(A) W1 > W2 = W3
(B) W1 > W2 > W3
(C) W1 < W2 = W3
(D) W1 < W2 < W3
(A) 2 × 1016
(B) 5 × 106
(C) 1 × 1017
(D) 4 × 1015