Procedure This experiment does not require high voltage source. It is recommende

Question

Procedure This experiment does not require high voltage source. It is recommended that you use Set R, (the approximately 5V. Check that the apparatus is set up as indicated in i Heathkit resistance substitution box) to 4.7 kO. We begin with RG 5 k12; and as a more precise balance is obtained, we w decrease gradually to zero. An attempt should be made to balance the bridge as close to the 50-cm mark along the slide wire as possible You will now determine the value of the unknown resistance Rx. Initially, the point of contact C should be made at the 50 cm mark so that R2R (L2L). R should be adjusted as accurately as possible to obtain a balance point. Tap the wire for a fraction of a second and note the amount of deflection of the galvanometer needle. Change the value of Ri and tap once again to see if the galvanometer deflects the same way or the opposite way. Continue the procedure until you succeed in finding two values of the resistance Ri that give oppositely directed galvanometer deflections. The balance point must lie between these values. Remember, Ro should gradually be decreased as finer balancing is achieved When the adjustment of Ri is completed, vary the slice point C to obtain a still more accurate balance. For your final balance, make RG 0 by placing a lead across the terminals of the resistance substitution box. Record the value of Ri, L2, and L3. Calculate a value for the unknown resistance. Be sure to reset RG-5 k before measuring the next resistance 1. Measure the resistance of the Heathkit resistance substitution box following the procedure described above. Determine the percent error between the actual resistance value and your experimental one 2. Reset Rx (the Heathkit resistance substitution box) to 470 and repeat step 1 3. Measure the resistance between the terminals 2 and 3, or 3 and 4, or 4 and 5, on the unknown resistance spool as in Step 1. The type and length of wire of which the spool is ade is indicated. The actual resistance value of the spool can be determined by obtaining values for , the cross-sectional area A from you instructor, and by using equation 8.1. Compare this to the value determined experimentally 4. Report any broken equipment to your instructor. Clean up your work area when finished Questions 1. Why is it beneficial to balance the Wheatstone bridge as closely as possible to the 50-cm mark along the slide wire? (Hint: The probe has a finite width and the accuracy of measuring L2 and Lj depends on this width.) To determine an unknown resistance, which is more accurate: Ohm's law or Wheatstone bridge method? Explain your answer Does it matter if the current supplied by the power supply is not constant? 2. 3.

Explanation / Answer

2) In case of Ohm's law method, accuracy of measurement depend on many factors such as accuracy with which current is measured , accuracy with which fixed voltage is known and callibration of the measuring instruments(ohmmeter etc).

Wheatstone bridge simply based on balancing the two arms. The meter should be accurate at only one point i.e. zero(in case of ohm's law method meter should be accurate at wide range of currents). If Resistances are known with accuracy , there is very less chance of error in measurement. Hence wheatstone bridge method is more accurate.

3) If once bridge is balanced then current supply or voltage will not affect the experiment as it works at zero voltage/current level.

Related Questions

Navigate

• Browse (All)
• Browse P
• Subjects

---

---

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.