Physics II-A Review Session

Hot water of 200 [g], 350 [K] is added to cold water of 100 [g], 280 [K]. Specific heat capacity of water is 4.18 [J/gK]. What equation(s) should you use to calculate the change of entropy of the system?

Answer explanation

Calculate the change in entropy using the formula ΔS = mcΔT, where m is the mass, c is the specific heat capacity, and ΔT is the change in temperature. Then sum up the entropy changes of both the hot and cold water to get the total change in entropy of the system.

To calculate the heat quantity which is necessary for 50 [g] ice at 0[°C] to melt to be 30 [°C] water when the heat of fusion is 333 [J/g] and specific heat capacity is 4.18 [J/gK], what equation(s) should you use?

Answer explanation

To calculate the heat quantity, first find the heat required to melt the ice: 50g * 333J/g = 16650J. Then, find the heat required to raise the temperature of the water from 0°C to 30°C: 50g * 30°C * 4.18J/gK = 6270J. Add both values to get the total heat quantity: 16650J + 6270J = 22920J.

Gas is enclosed in cylinder. When 20 [N] force is added to piston, the gas is compressed 0.3 [m]. If heat does not escape outside, what equation(s) should you use to calculate the increase of internal energy of the gas?

Answer explanation

The increase in internal energy of the gas can be calculated using the formula: ΔU = W + Q, where W is the work done on the gas (W = F * d) and Q is the heat added. Given F = 20 N and d = 0.3 m, we can calculate W = 20 N * 0.3 m = 6 J. Since no heat escapes, Q = 0. Therefore, ΔU = 6 J.

Two capacitors, C₁, C₂ and a battery are connected as below. The capacitance of C₁ is 470 [μF] and its conducting plates are 1.00 [mm] apart. The capacitor C₂ has the same shape as C₁, but the plates are apart 1.50 [mm]. The voltage of the battery is 15.0 [V]. To calculate the capacitance of C₂. what equation(s) must you use?

Answer explanation

(1) Using the formula C = ε₀ * A / d, the capacitance of C% is calculated to be 313.33 μF. (2) The resultant capacitance is 783.33 μF. (3) The charge stored in C' is 7.05 mC. (4) The voltage applying to C' is 31.91 V. (5) When a metal plate is inserted, the voltage applying to C% is 15 V.

The circuit contains a 100-turns coil which cross-section is 2.00×10^-3[m²], and a resistance of 10.0 [Ω]. When the magnetic flux density, B, is increasing 0.100 [T] per second what equation(s) must be used to calculate the electromotive force, V_emf?

Answer explanation

To calculate Vemf, use Faraday's Law: Vemf = N * A * dB/dt = 100 * 2.00e-4 * 0.100 = 0.200 V. To find power, use P = V^2 / R = (0.200)^2 / 10.0 = 0.004 W.

Two charges with 1.2×10[C] and -0.3×10[C] placed 1 [m] apart. The proportional constant, k_C, is 8.99×10⁹[Nm²/C²]. To calculate the force the objects affect each other at what equation(s) should you use?

Answer explanation

(1) Use Coulomb's law to calculate the force between the charges. (2) Use the formula for electric field to find the electric field at point P.

There is a charge A of 3.5×10^-6[C]. To calculate the electric potential, V, at a point which is 1.1 [m] apart from the charge what equation(s) should you use?

Answer explanation

(1) V = k * q / r = (9 x 10^9) * (3.5 x 10^-6) / 1.1 = 28.64 V. (2) U = k * q1 * q2 / r = (9 x 10^9) * (3.5 x 10^-6) * (4.5 x 10^-6) / 0.3 = 47.25 J.

There are two wires A and B placed perpendicular to the paper. 0.100 [A] of electric current flows the wire A and B, but their directions are opposite. To calculate the magnitude and the direction of magnetic field at origin generated by the electric current flowing through wire A, what equation should you use?

Answer explanation

(1) The magnitude of the magnetic field at origin due to wire A is calculated using Ampere's law. (2) The resultant magnetic field at origin is the vector sum of the fields due to wires A and B. (3) The resultant magnetic field at point C is the vector sum of the fields due to wires A and B.