Waec Physics 2009 Past Questions and Answers

Question 36:

• WAEC 2009

An isolated metal sphere of radius R, carrying an electric charge Q, is situated in the medium of relative permitivity, E_r. A test charge is placed at a point p, distance r from the surface of the sphere. Let E_o represent the permitivity of free space. The magnitude of the electric field intensity at P is given by the expression

A. $\frac{Q}{4\pi E_o{E}_r{r}^2}$
B. $\frac{Q}{4\pi E_o{E}_r(R+r{)}^2}$
C. $\frac{Q}{4\pi E_o{E}_r(R-r{)}^2}$
D. $\frac{Q}{4\pi E_o{E}_r{R}^2}$

Question 37:

• WAEC 2009

A resistor of resistance R is connected to a battery of negligible internal resistance. If a siilar resistor is connected in series with it the

A. Effective resistance of the circuit is halved
B. Total power dissipated is doubled
C. Total current in the circuit is halved
D. Terminal voltage is halved

Question 38:

• WAEC 2009

A cell of e.m.f. 1.5V is connected in series with a resistor of resistance 3.0$\mathrm{\Omega }$. A voltmeter connected across the cell registers 0.9V. Calculate the internal resistance of the cell

A. 2.0$\mathrm{\Omega }$.
B. 3.0$\mathrm{\Omega }$.
C. 5.0$\mathrm{\Omega }$.
D. 6.0$\mathrm{\Omega }$.

Question 39:

• WAEC 2009

A wire of resistivity 4.40 x 10^-5$\mathrm{\Omega }$ cm has a cross sectional area of 7.50 x 10^-4 cm². Calculate the length of the wire that will be required to make a 4.0$\mathrm{\Omega }$ resistor

A. 82.50 cm
B. 68.18cm
C. 15.90cm
D. 11.95cm

Question 40:

• WAEC 2009

A battery of e.m.f. 12.0V and internal resistance0.5$\mathrm{\Omega }$ is connected to 1.5$\mathrm{\Omega }$ and 4.0$\mathrm{\Omega }$ series resistor. Calculate the terminal voltage of the battery.

A. 13.0V
B. 11.0V
C. 3.0V
D. 1.0V