This physics problem tests your understanding of fundamental physical laws and their applications. The step-by-step solution below breaks down the problem using relevant equations and physical reasoning.
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Here are the solutions for questions 17 through 21, and the equivalent resistance calculation. 17. Given: Focal length, f = 20 cm Step 1: Convert the focal length from centimeters to meters. f = 20 cm = 0.20 m Step 2: Use the formula for the power of a lens (P), which is the reciprocal of the focal length in meters. For a converging lens, the focal length is positive. P = (1)/(f) Step 3: Substitute the value of f and calculate the power. P = (1)/(0.20 m) P = +5.0 D The correct option is B. The final answer is +5.0 D. 18. Given: Radius of curvature, R = 2 m Step 1: Recall the relationship between the focal length (f) and the radius of curvature (R) for a mirror. f = (R)/(2) Step 2: For a convex mirror, the focal length is conventionally negative. f = -(R)/(2) Step 3: Substitute the value of R and calculate the focal length. f = -2 m2 f = -1 m The correct option is C. The final answer is -1 m. 19. Ohm's law states that the voltage (V) across a conductor is directly proportional to the current (I) flowing through it, provided all physical conditions and temperature remain constant. The constant of proportionality is the resistance (R). The correct expression for Ohm's law is V = IR. The correct option is A. The final answer is V = IR. 20. The resistance (R) of a wire is given by the formula R = (L)/(A), where is the resistivity of the material, L is the length of the wire, and A is its cross-sectional area. From this formula, resistance is directly proportional to length. Therefore, an increase in length will increase the resistance of the wire. The correct option is D. The final answer is increase in length. 21. The SI unit of electric current is the ampere (A). The correct option is B. The final answer is ampere. For the equivalent resistance calculation shown in the image: The circuit shows three 2 resistors connected in parallel. Step 1: Use the formula for equivalent resistance (R_eq) of resistors in parallel. (1)/(R_eq) = (1)/(R_1) + (1)/(R_2) + (1)/(R_3) Step 2: Substitute the given resistance values. (1)/(R_eq) = (1)/(2 ) + (1)/(2 ) + (1)/(2 ) Step 3: Add the fractions. (1)/(R_eq) = (1+1+1)/(2 ) (1)/(R_eq) = (3)/(2 ) Step 4: Invert the result to find R_eq. R_eq = (2)/(3) Step 5: Convert the fraction to a decimal. R_eq ≈ 0.666... R_eq ≈ 0.67 The calculation shown in the image for R_eq is incorrect in its initial setup (1 - (1)/(2) + (1)/(2) + (1)/(2) ), but the final numerical value of 0.67 is correct for three 2 resistors in parallel. Last free one today — make it count tomorrow, or type /upgrade for unlimited.