Electrical Engineering > EXAM > EE 101L Circuits 1 (GRADED A) QUESTIONS AND PROBLEMS-EX01 | Already Graded A+ (All)

EE 101L Circuits 1 (GRADED A) QUESTIONS AND PROBLEMS-EX01 | Already Graded A+

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EE 101L Circuits 1 (GRADED A) QUESTIONS AND PROBLEMS-EX01 QUESTIONS AND PROBLEMS: (ANSWERS) 1. Describe the type of meter movement used in analog meters. An analog meter is a coil experiencing a torque. Since it is a torque, the pointer deflects the current of the circuit and its direction changes as the flow of the current changes. 2. What device is used to extend the range of a DC ammeter and how is it connected to the basic meter? The device used to extend the range of a DC ammeter is called shunt (resistors connected in parallel) in which it allows electric current to pass around another point in the circuit by creating a low resistance path. Also, the resistor must be placed which is parallel to ammeter to adjust the current flow without affecting the voltage of the circuit. 3. What device is used to extend the range of a DC voltmeter and how is it connected to the basic meter? The device used to extend the range of a DC voltmeter is called multiplier resistor (resistors connected in series). A resistor must be added in series to adjust its voltage of the circuit without affecting its current. 4. Why is it necessary that an ammeter be a low resistance instrument? Why must a voltmeter be a high resistance instrument? It is necessary that an ammeter must have a low resistance to avoid change of current measured in series connection, while a voltmeter must have high resistance to avoid appreciable effect on the voltage of the circuit to avoid change of current that it will measure measured in parallel connection. 5. What type of basic meter is configured as a wattmeter? In wattmeter, there are two coils which are placed in parallel and the other one is in series. The pointer is relative to the coils that results the magnitude of power which is equal to its current and voltage. 6. Two 150V voltmeters are being compared; meter A has 5K|/ V while meter B has a total meter resistance of 750 K|. Which is the more sensitive meter? Why? Sensitivity of the voltmeter is equal to the quotient of resistance and voltage. Hence, 750 K|/150 V = 5K|/ V then, meter A and meter B have the same sensitivity. 7. What current is required to full scale deflection of a galvanometer having a current sensitivity of 50 μ A per scale division? The meter has exactly 50 divisions on either side of the mid-scale index. The current required to full scale deflection of a galvanometer is 2500 μ A since (50 μ ) x (50) is equal to that. 8. What potential difference appears across the galvanometer described in problem 6 when the pointer is fully deflected? The meter resistance is 10 |. Voltage is equal to the product of the reciprocal of the voltmeter sensitivity to its resistance. Thus, (5 K|/V) x (10 |) is equal to 2mV. 9. Determine the series resistance needed to convert a galvanometer to voltmeter reading 15 V on full scale deflection if a current of 2.5 mA causes full scale deflection and the resistance of the coil is 10 |. Given: VT =15V Im=2.5 mA Rm=10 Ω Solution: Voriginalmeter max=I m x Rm Voriginal meter max=2.5 mA x 10 Ω V originalmetermax = Rmeter V adjusted metermax Rmeter + Rseries V =2.5 mV 25 mV = 10 Ω originalmeter max 15 V 10 Ω+ R series Rs =5990 Ω 10. Determine the shunt resistance needed to convert a galvanometer to an ammeter with a full scale reading of 10 A if the scale requires 2.5 mA to cause full deflection with a coil resistance of 10 |. Given: IT =10 A Im=2.5 mA RT =10 Ω Solution: I originalmeter max = Rshunt I adjusted meter max Rmeter + Rshunt

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