Magnetic Effects of Electric Current — Science STD 10 — Question

A concave mirror has a focal length of 25cm. At which of the following distance should a person hold his face from this concave mirror so that it may act as a shaving mirror?

1. 45cm
2. 20cm
3. 25cm
4. 30cm

Give reason for your choice.

Which of the following represents voltage?

When an electric lamp is connected to 12V battery, it draws a current of 0.5A. The Power of the lamp is:

1. 0.5W.
2. 6W.
3. 12W.
4. 24W.

The real image formed by a concave mirror is larger than the object when object is:

1. At a distance equal to radius of curvature.
2. At a distance less than the focal length.
3. Between focus and centre of curvature.
4. At a distance greater than radius of curvature.

Which of the following ray diagrams is correct for the ray of light incident on a concave mirror as shown in Figure?

Materials that allow electrons to flow through them are known as:

At the time of short circuit, the electric current in the circuit:

n order to obtain a magnification of, −0.6 (minus 0.6) with a concave mirror, the object must be placed:

1. At the focus.
2. Between pole and focus.
3. Between focus and centre of curvature.
4. Beyond the centre of curvature.

A student obtained a sharp image of the grills of a window on a screen using a concave mirror. His teacher remarked that for getting better results a well lit distant object (preferably the sun) should be focussed on the screen. What should be done for this purpose?

The most suitable material for making the core of an electromagnet is: