Current Electricity — Physics STD 12 Science — Question

A long straight wire carries a current of 35 A. What is the magnitude of the field B at a point 20 cm from the wire?

If heavier bodies are attracted more strongly by the earth, why don't they fall faster than the lighter bodies?

A person has near point at 100cm. What power of lens is needed to read at 20cm if he/ she uses.

1. Contact lens,
2. Spectacles having glasses 2.0cm separated from the eyes?

In a children's park, there is a slide which has a total length of 10m and a height of 8.0m (figure). Vertical ladder are provided to reach the top. A boy weighing 200N climbs up the ladder to the top of the slide and slides down to the ground. The average friction offered by the slide is three tenth of his weight. Find

1. The work done by the ladder on the boy as he goes up.
2. The work done by the slide on the boy as he comes down. Neglect any work done by forces inside the body of the boy.

A beam of light having wavelengths distributed uniformly between 450nm to 550nm passes through a sample of hydrogen gas. Which wavelength will have the least intensity in the transmitted beam?

A galvanometer coil has a resistance of 15 Ω and the metre shows full scale deflection for a current of 4 mA. How will you convert the metre into an ammeter of range 0 to 6 A?

Explain briefly, with the help of a circuit diagram, the transistor action of npn transistor in CE configuration. Draw the typical shapes of input and output characteristics.

Identify the following electromagnetic radiations as per the wavelengths given below.
Write one application of each.

1. 10^–3 nm
2. 10^–3 m
3. 1 nm