When the current flowing through a lamp is decreased by 2%, then the percentage change in the power consumed by the lamp will be Only one correct answerA.5.48%B.4.25%C.3.96%D.6.75%

By what percentage will the illumination of the lamp decrease if the current drops by 20% ?

If the voltage connected across a resistor is decreased by 50%, then the power dissipated across it willOnly one correct answerA.Reduced to 25%B.Reduced to 50%C.Reduced to 75%D.Reduced to 80%

What is the percentage loss of energy as heat in incandescent bulbs?*90%20%95%60%

A lamp is switched on for 2.0 hours. The power input to the lamp is 1.0 W. The energy given outby the lamp as light is 7.0  10 3 J.How much energy is converted to other forms by the lamp?A 120 J B 200 J C 3400 J D 7200 J

17 Researchers have developed a new type of filament lamp with an efficiency of 40%. Old-typefilament lamps have an efficiency of 5.0%. The two types of lamp produce the same useful outputpower.What is the ratio input power to new type of lampinput power to old type of lamp ?A 0.13 B 0.63 C 1.6 D 8.018 A student attempts to derive the formula for kinetic energy EK . She begins by considering anobject of mass m which is initially at rest. A constant force F applied to the object causes it toaccelerate to final velocity v in displacement s. The kinetic energy gained by the object is equal tothe work done on the object by the force F.Which equation would the student not need in order to derive the formula for EK ?A F = ma B W = Fs C E = Fs21 D v 2 = u 2 + 2as19 A metal wire obeys Hooke’s law and has a Young modulus of 2.0  10 11 Pa. The wire has anoriginal length of 1.6 m and a diameter of 0.48  10 –3 m.What is the spring constant of the wire?A 7.2  10 3 N m–1B 2.3  10 4 N m–1C 2.9  10 4 N m–1D 9.0  10 4 N m–120 A wire is being stretched by a tensile force.Which statement about the elastic limit must be correct?A The deformation is plastic after the elastic limit has been reached.B The deformation is plastic until the elastic limit is reached.C The extension is proportional to the tensile force after the elastic limit has been reached.D The extension is proportional to the tensile force until the elastic limit is reached.21 Which statement is correct for all types of progressive wave?A The distance from a peak to the next trough is equal to a wavelength.B They can be demonstrated in ripple tanks.C They consist of vibrating atoms.D They transfer energy from one position to another