In an electric bell, when the metal strip gets attached to the electromagnet , it no longer touches the interrupter , and hence the circuit breaks.

A metallic bob A oscillates throgh the space between the poles of an electromagnet . The oscillation are more quickly damped when the circuit is on, as compared to the case when the circuit is off. Explain.

Electric fuse is a protective device used in series with an electric circuit or an electric appliance to save it from damage due to overheating porduced by strong current in the circuit or application. Fuse wire is generally made from an alloy of lead and tin, which has hifh resistance and low melting point. It is connected in series in an electric installation. If a circuit gets accidentally short-circuited, a large current flows, then fuse wire melts away, which causes a break in the circuit. The power through fuse (F') is equal to heat energy lost per unit area per unit time (h) (neglecting heat loses from ends of the wire). P = I^2R = h xx 2pirl [R = (rhol)/(pir^2)] where r and l are the length and radius of fuse wire, respectively. A Battery is described by its emf (E) and internal resistance (r). Efficiency of battery (eta) is defined as the ratio of the output to the input power. eta = (Output power)/(Input power) xx 100% But I= E//(R+r), input power = EI. Output power = EI - I^2r , then. eta = ((EI - I^2r)/(EI)) xx 10 (1-(Ir)/E) xx 100 =1 - (E/(R+r)) (r/E) xx 100 = (R/(R+r)) xx 100 We know that output power of a source is maximum when the external resistance is equal to internal resistance, i.e., R = r . Efficiency of a battery (nonideal) when delivering the maximum power is

Electric fuse is a protective device used in series with an electric circuit or an electric appliance to save it from damage due to overheating porduced by strong current in the circuit or application. Fuse wire is generally made from an alloy of lead and tin, which has hifh resistance and low melting point. It is connected in series in an electric installation. If a circuit gets accidentally short-circuited, a large current flows, then fuse wire melts away, which causes a break in the circuit. The power through fuse (F') is equal to heat energy lost per unit area per unit time (h) (neglecting heat loses from ends of the wire). P = I^2R = h xx 2pirl [R = (rhol)/(pir^2)] where r and l are the length and radius of fuse wire, respectively. A Battery is described by its emf (E) and internal resistance (r). Efficiency of battery (eta) is defined as the ratio of the output to the input power. eta = (Output power)/(Input power) xx 100% But I= E//(R+r), input power = EI. Output power = EI - I^2r , then. eta = ((EI - I^2r)/(EI)) xx 100 = (1-(Ir)/E) xx 100 =[1 - (E/(R+r)) (r/E)] xx 100 = (R/(R+r)) xx 100 We know that output power of a source is maximum when the external resistance is equal to internal resistance, i.e., R = r . Two fuse wires of same potential , material have length ratio 1:2 and ratio of radius 4:1 . Then respective ratio of their current rating will be

Electric fuse is a protective device used in series with an electric circuit or an electric appliance to save it from damage due to overheating porduced by strong current in the circuit or application. Fuse wire is generally made from an alloy of lead and tin, which has hifh resistance and low melting point. It is connected in series in an electric installation. If a circuit gets accidentally short-circuited, a large current flows, then fuse wire melts away, which causes a break in the circuit. The power through fuse (F') is equal to heat energy lost per unit area per unit time (h) (neglecting heat loses from ends of the wire). P = I^2R = h xx 2pirl [R = (rhol)/(pir^2)] where r and l are the length and radius of fuse wire, respectively. A Battery is described by its emf (E) and internal resistance (r). Efficiency of battery (eta) is defined as the ratio of the output to the input power. eta = (Output power)/(Input power) xx 100% But I= E//(R+r), input power = EI. Output power = EI - I^2r , then. eta = ((EI - I^2r)/(EI)) xx 100 = (1-(Ir)/E) xx 100 =[1 - (E/(R+r)) (r/E)] xx 100 = (R/(R+r)) xx 100 We know that output power of a source is maximum when the external resistance is equal to internal resistance, i.e., R = r . The maximum power rating of a 20.0 Omega fuse wire is 2.0 kW. This fuse wire can be connected safely to a DC source (negligible internal resistance) of

An automatic electrical switch that breaks the circuit when excess current passes through it

when an earthed electric appliance gets shor circuited, then the current from its metal body flows into the

An electrometer consister of a fixed vertical metal bar OB at the top of which is attached a thin rod OA which gets deflected from the bar under the action of an electric charge (fig.). The rod can rotate in vertical plane about fixed horizontal axis passing through O. The reading is taken on a quadrant graduated in degrees. The length of the rod is l and its mass is m. what will be the charge when the rod of such an electrometer is deflected through an angle alpha in equilibrium. Find the answer using the following two assumptions : The charge on the electrometer is equally distributed between the bar & the rod and the charges are concentrated at point A on the rod & at point B on the bar.

A potentiometer circuit is shown in Figure 3. AB is a uniform metallic wire having length of 2 m and resistance of 8Omega . The batteries E_(1) and E_(2) have emfs of 4V and 1.5 V and their internal resistance are 1Omega" and "2Omega respectively. When the jockey J does not touch the wire AB, calculate : (a) the current flowing through the potentiometer wire AB. (b) the potential gradient across the wire AB.

A currrent I is passed through a silver strip of width d and area of cross section A. The number of free electrons per unit volume is n. (a) Find the drift velocity v of the electrons. (b) If a magnetic field B exists in the region as shown in what is the average magnetic force on the free electrons? (c) Due to the magnetic force, the free electrons get accumulated on one side of the conductor along its length. This produces a transverse electric field in the conductor which opposes the magnetic force on the electrons. Find the magnitude of the electric field which will be the potential diference developed across the width of the conductor due to the electron- accumulation? The appearance of a transverse emf, when a current-carrying wire is placed in a magnetic field, is called hall effect.

The figure shows a glass container filled with air and having an electric bell kept inside it. A person standing close to it can distinctly hear the bell. Now the air inside is removed slowly. How does the speed of sound get affected when there is an increase of moisture in the air?