Related InterviewSolutions

• A voltmeter with a resistance of `8000Omega` is used to measure the emf of a cell of internal resistance `4Omega`. What is the percentage error in the reading of the voltmeter?
• An ammeter and a voltmeer are connected as in figures in order to measure an unknown resistance. Justify quantitatively which connection is to be perfected.
• Two tangent galvanometer of 50 and 100 tunrs of the same wire and radii 10cm, and 5cm respectively are connected in parallel. Calculate the ratio `tan(theta_(1)`:`tan(theta_(2)` where `theta_(1)` and `theta(2)` are the deflections produec in them.
• It is required to measure the resistance ofa circuit operating at 120V. There is only one galvanometer of current sensitivity `10^(-6)` A per division. How should the galvanometer be connected in the circuit to operate as an ohmmeter? What minimum resistance can be measured with such a galvanometer if its full scale has 40 division? Construct the entire scale of such an ohmmeter in ohms per 5 division? Neglect galvanometer resistance.
• When the modified galvanometer of exercise 26 is connected across the terminals of a battery, it shows a current of 4A. The current drops to 1A when a resistance of `1.5Omega` is connected in series with the modified galvanometer. Find the emf and the internal resistance of the battery.
• A 600`Omega` resistor and a 400`Omega` resistor are connected in series across a 90-volt line. A voltmeter acros the `600Omega` resistor reads 45V. What is the value of the voltmeter resistance? If the same voltmeter is connected across the `400Omega` resistor, what will be its reading?
• A moving coild galvanometer with a lamp-and-scale arrangement has a coil of 50 turns of mean area 1.5 `cm^(2)` per turn and the effective strength of the field (radial) is 0.02T. If a current of `10^(-9)` A produces a deflection of 1 cm on a scale placed at 1 m away, calcualte the steady torque required to hold the suspension twisted through 1 radian.
• A galvanometer with a coil resistance of `100Omega` shows a full-scale deflection when a current of 1 mA is passed through it. What is the value of the resistance which can convert this galvanometer into an ammeter showing a full-scale deflection for a current of 10A? A resistance of the required value is available but it will get burnt if the energy dissipated in it is greater than 1W. Can it be used for the conversion of the galvanometer described above? [Hint:Power dissipated =`I^(2)`watt)
• Three voltmeters A, B and C have the same range but different resistances `R_(A)`=`1200Omega`, `R_(B)= 1000Omega`` and `R_(C)=800 Omega. A is connected in parallel to C and B is connected in series with the combination of A and C. When the combination of ABC so formed is connected across a constant potential difference `V_(ab_)` meter A reads 4.8V and meter B reads 10 volts. What will be the reading of each meter when they are all connected in series across the same potential difference `V_(ab)`?
• A millimmater of resistance `20Omega` reads up to 50 mA. Explain how the instrument can be used to read a) currents up to 5A, b) voltages up to 50V.