Jul 262013
 


Torque on a rectangular coilLet us consider a rectangular coil PQRS of length ‘l’ and breadth ‘b’ suspended in uniform horizontal magnetic field ‘B’. Let the plane of the coil make an angle ‘θ’ with the direction of magnetic field.

When current ‘I’ is passed through the coil, the magnetic force produced on the various arms of the coil are:

i) Force on arm PQ,

F1 = IlBsinθ
     = IlBsin90o
     = IlB
F1 is perpendicular to both l and B and is directed outwards.

ii) Force on arm QR,

F2 = IbBsinθ
∴ F2 is perpendicular to both b and B and is directed downwards.

iii) Force on arm RS,

F3 = IlBsinθ
     = IlBsin90o
     = IlB
∴ F3 is perpendicular to both l and B and is directed inwards.

iv) Force on arm SP,

F4 = IbBsinθ
∴ F4 is perpendicular to both b and B is directed upwards.

torque on a rectangular coil 2The forces F2 and F4 are equal and opposite and they pass through same line of action, so they cancel each other resulting to no torque or force on the coil.
The forces F1 and F3 are also equal and opposite but they pass through different lines of action, so they constitute couple or torque which is given by:

τ = (F1 or F3) × Arm of couple
   = IlB × bcosθ
   = IBAcosθ [∵ A = l × b]

If there are ‘N’ number of turns in the coil, then the total torque is:
   τ = N × IBAcosθ
∴ τ = BINAcosθ

Special Cases:
i) If θ = 0o, τ = BINA (maximum value)
When the plane of the coil is kept parallel to the magnetic field, torque on the coil is maximum.
ii) If θ = 90o, τ = 0 (minimum value)
When the plane of the coil is kept perpendicular to the magnetic field, torque on the coil is minimum.

Yoshiro Mori

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Jul 222013
 

yoshiro moriYoshiro Mori, the winner of Padma Bhushan Award in 2004 was born in 14 July 1937 in Nomi, Ishikawa, Japan. He was born in wealthy family of Shigeki and Kaoru Mori. His mother died when she was seven due to long period of illness and his father died in 1989. Their family is greatly influenced by politics.

Famous as: Prime Minister of Japan
Born on: 14 July 1937
Born in: Nomi, Ishikawa, Japan
Nationality: Japan
Works and Achievements: Industrialization of Japan, Padma Bhushan Award (2004)


Talking about the educational background, he received degree from Waseda University where he developed many qualities for polishing his personality like independence, sense of responsibility and so on. He joined the University’s oratorical society where he started to learn politics.

He met many great political personalities and great orators at the same university and shaped his dream to become politician. He married with his fellow student of Waseda University, Chieko Maki in 1961 and had two children. His son is Yuki and daughter is Yoko. He was the Rugby player and never smoke due to his sportsmanship and family’s teaching. He is often referred as ‘Rugby Prime Minister’.

He started the work of reporting on a major newspaper of Japan which helped him for continuing in politics. He becomes a Secretary of a Diet member after leaving the job in 1962. Mori first time stood for election and was elected in the lower house in 1969 when he was 32. He had elected for about 10 times and joined the Labor Democratic Party.

He assumed the office of the Education Minister in 1983 and worked on several education reforms. He was again elected in International trade and industry minister in 1992 and become construction minister. He has got many important positions in Labor Democratic Party and become secretary general twice a time. He was also the chairperson of the Policy Research Council and introduced many major policies.

He was elected the Prime minister of Japan on 2 April 2000 and reelected again the remained in the position. His period of Prime minister is mainly notable for his ‘slips of tongue’ and unpopular decisions.