Page 1 :
Aim: To compare e. m, f. of the two given cells using a potentiometer., Apparatus: A potentiometer, a plug key, a rheostat, two cells, jockey, four way key, battery, galvanometer, connecting wires etc., , , , , , , , , , , , , , Diagram:, 4 K, E,, 0)", A E,_K,, 0 TT |, 200!, an TAT MMTATMTTTTTTATTT 300, , , , , , 4.0) PLALLLLLLLLLLUL LAUD LLU Rh, , aa, <1? lable, Rh Es- Batt, , 6,.6,- al, Fae Galvanome ey Ku ow gh- Khaw, , , , , , =) [+ 5, EE) EO (Difference), , , , , Formula:, , 1) Individual cell method or Separate cell method —, Fy bt, E, L, ., Where, L, is the balancing length when cell E, is in the circuit and L, is the balancing length when, , cell E, is in the circuit., , 2) Sum and difference method —, E+B, Zh, E,_K+hL, Be lL, bal,, , Where, L, is the balancing length when both cells assist€ach other i.e. E,+ E, (sum method) and, L, is the balancing length when both cells oppose each other i.e. E,- E, (difference method)., , Procedure:, , Part — I (Individual cell Method or Separate cell method), , 1. Care has to be taken that E, > E, ., , 2. Connect the circuit as shown in fig.(i). Close the key K to, current will start flowing. Adjust the rhcostat at minimum resistance for maximum curr, the circuit., , 3. Take the cell E, in the circuit by closing key K,. Then touch the jockey at ze!, potentiometer wire and note the direction of deflection in the galvanometer, Touc, at the other end of the potentiometer wire. If the direction of deflection is opposite, the first case, the connections are correct. (If the deflection is in the same direction the!, , bring the circuit in working, %, ent 10, , ro end of the, h the jockey, to that 0, n either, , , , >cannea witn Gamscdann

Page 2 :
connections are wrong or c.m.f. of the cell used is less). Starting from the point A touch the, jockey on the wire at various points and obtain the null point P,. Note the length L, of the, potentiometer wire between the Point A and P. ., , 4, Now disconnect the cell E, by opening key K,. And connect the cell E,by closing key K,, Obtain the null point P, and note the length L, of the potentiometer wire between the points A, & P,. Make sure that theostat position is same as in step 2., , 5, Repeat the observations alternately for each cell again by adjusting the rheostat at different, positions., , part -II (Sum and difference method), ]. Care has to be taken that E,>E,., , 2, Connect the circuit as shown in fig.(ii) such that the positive terminal of E, is connected to the, negative terminal of E,. In this case both cells assist each other i.e, sum method. Close the key, K to bring the circuit in working, as current will start flowing. Adjust the rheostat at minimum, resistance for maximum current in the circuit. . . ., , +80 Then touch the jockey’at zero end of the potentiometer wire and note the direction of deflection, , , inthe galvanometer. Touch the Jockey at the other end of the potentiometer wire. If the, direction of deflection is opposite to that in the first case, the connections are correct. (If the, deflection is in the same direction then cither connections arewrong.or e.m_f. ofthe cell used, , ag’ is less). Starting from’the point A touch the jockey on the wire at various points and obtain: the, null point P,. Note.the length L, of the potentiometer wire between the point A and P1., , , Now.connect cells, such that the‘negative terminal of E, is connected to the negative terminal, of E,. In this case botli‘cells oppos¢ each other ie. difference method. Obtain the null point P,, and note the length L, of the, potentiometer wire between the points A & P,. Make sure that, thcostat position is same as in step 2. , ~S.r-Repeat the observations for'cach*sum and differerite’ method: by adjusting ‘the theostat at, different positions. sa ,, , ,, , , , , , Observations: ra. MS f a FEN aT ', E.M.F. of battery, t, E.M.E.of celb, E, Noite 1B e ry «), ae ., , EMF. of cell, B,=_ |B Vor, , Part — I (Individual cell Method or Separate cell method), , , , , , , , , , , , , , , , , , , , Balancing length when | Balancing length when, Obs. Nc & E, is fie ae E, is jibe ah AES, LO-* L. (cm) : L, (em) & 4, 1| 276 | 2To | jt eo2z 2a, Z| 23 289 tg 2B, 4[ 296 | ago, oe, 14 3ads Sol | “[:oe>, | SIZ BJ ' Powe, , , , , , , , , , , , _ Bo 0l98, , scanned with Lamscann