The unknown resistance of a conductor can be determined by Wheatstone bridge. The standard form of Wheatstone bridge is shown in the figure. It can be shown when the bridge is balanced.

\(\frac { P }{ Q } =\frac { R }{ S } \quad or\quad S=\frac { Q }{ P } R\)
Knowing P,Q and R, unknown resistance S can be calculated.
Read the above passage and answer the following questions.
(i) Name any two applications of Wheatstone bridge.
(ii) What is the practical utility of the post office box in day to day life?

Vishwajeet purchased cells for his transistor. He felt that cells are not working properly. He wanted to check their emf. So, he took the cells to the physics lab and with the help of potentiometer found their emf. To his surprise, emf was less than the value claimed by the manufacturer. He lodged the complaint with consumer forum and received the deserving response.
Read the above passage and answer the following question.
(i) What values are displayed by Vishwajeet?
(ii) Why do you think Vishwajeet used potentiometer instead of voltmeter to find out emf of the cell? For more precise measurement, the potential gradient of the potentiometer should be high or low?

Ramaniamma was a childless window. She ran her life only by the pension for the Sr. citizens from the Government. When she switches ON one bulb in her house, all the other appliances get switched OFF. She could not even spend for an electrician. Sujatha living nearby decided to do something for her. She referred to Physics books and learned that the series combination for the household connection could be the reason. She called an electrician and had the circuit changed to parallel combination. The problem was solved and Ramaniamma was happy. She thanked Sujatha for her help to solve the problem.
Read the above passage and answer the following questions.
(i) What are the values possessed by Sujatha?
(ii) Why a parallel combination is used for household? Give two advantages.

That night Vaikunth was preparing for his physics exam. Suddenly, the light in his room went off and he could not continue his studies. His cousin brother Vasu who had come to visit him was quick to react. Vasu using the torch (an android application) installed in his mobile phone found that the fuse had blown out. He checked the wiring and located a short circuit. He checked the wiring and located a short circuit. He rectified it and put a fuse wire. The light came to life again. Vaikunth had a sign of releif and continued his studies.
Read the above passage and answer the following question.
(i) What are the values projected by Vaikunth and Vasu?
(ii) Why did Vasu have to check the wiring?
(iii) What is an electric fuse? What characteristics you would prefer for a fuse wire?