JAMB Physics Past Questions & Answers - Page 9

 W = mg = 0.5 x 10 = 5 N

 Since it's light, neglect the weight of the metre rule.

 The effective tension T acting in the vertical direction = T sin 30°

 From the second condition of equilibrium, sum of clockwise moments equal sum of anticlockwise moments

 Taking moment at E 

 ⇒ T sin 30° x 30 = 5 x 50

 ⇒ ∴T=250

 T = \(\frac{250}{15}\) = 16.67N 

Ep = 2.2kV = 2200V; Es=110V; Ns=25; Np=?

=\(\frac{E_p}{E_s}\) = \(\frac{N_p}{N_s}\)
 

= \(\frac{2200}{110}\) = \(\frac{N_p}{25}\)

=110 × Np = 2200 × 25

=\(N_p\) = \(\frac{55,000}{110}\)

∴\(N_p\) = 500 turns

The pinhole camera works on the principle of the rectilinear propagation of light. This principle states that light travels in straight lines. When light passes through the tiny hole in a pinhole camera, it forms an inverted image on the opposite side of the camera. The size of the image depends on the distance between the object and the pinhole

The S.I unit of heat capacity is JK-1 and it is an extensive property as it depends on the amount of substance present.

Therefore, (i) and (iv) only are not true

The patient cannot see clearly an object closer than 50 cm

Therefore, the patient needs a lens that would enable him see clearly, objects placed 25 cm from the lens

So, we take the object to a distance of 25 cm from the lens so that the image forms at 50 cm in front of the lens

u=25cm ;v=-50cm (virtual image); p=

\(\frac{1}{f}\)=\(\frac{1}{u}\) + \(\frac{1}{v}\)

⇒\(\frac{1}{f}\) =\(\frac{1}{50}\)

⇒\(\frac{1}{f}\) = \(\frac{1}{25}\)-\(\frac{1}{50}\)

⇒\(\frac{1}{f}\) = f = 50cm =0.5m

⇒\(\frac{1}{f}\) = \(\frac{2-1}{50}\)

   p = \(\frac{1}{f}\)

   p =  \(\frac{1}{0.5}\)

   p =   2 diopters 
 
  ; The patient needs a converging lens with a power of 2 diopters