Steady Current and DC Circuits

How the real exam tests it

Questions from real CSCA papers that test this concept. Work each one out before you open the answer.

1. CSCA Physics December 2025 Past Paper
   The total resistance when two resistors of $200 \Omega$ and $300 \Omega$ are connected in parallel is ( ).
   • A．$500 \Omega$
   • B．$600 \Omega$
   • C．$100 \Omega$
   • D．$120 \Omega$
   Show answer & solution

   Answer: D

   1 Parallel resistors: $1 / \mathrm { R } = 1 / 200 + 1 / 300 = ( 3 + 2 ) / 600 = 5 / 600$. 2 $\mathrm { R } = 600 / 5 = 120 \Omega$.
   See it in the full CSCA Physics December 2025 Past Paper
2. CSCA Physics March 2026 Past Paper
   Two resistors ( $2 \Omega$ and $8 \Omega$ ) connected in parallel have a total resistance of
   • A．$1.6 \Omega$
   • B．$2 \Omega$
   • C．$4 \Omega$
   • D．$10 \Omega$
   Show answer & solution

   Answer: A

   $1 / R = 1 / 2 + 1 / 8 = 5 / 8 , R = 1.6 \Omega$. Parallel resistance is always less than the smallest resistor ( $2 \Omega$ ), eliminating B, C, D. Answer: A.
   Take the full CSCA Physics March 2026 Past Paper — timed & graded
3. CSCA Physics April 2026 Past Paper
   A $100 \Omega$ resistor and a $200 \Omega$ resistor are connected in parallel. Their equivalent resistance is
   • A．$150 \Omega$
   • B．$50 \Omega$
   • C．$300 \Omega$
   • D．$66.7 \Omega$
   Show answer & solution

   Answer: D

   $\frac { 1 } { R } = \frac { 1 } { 100 } + \frac { 1 } { 200 } = \frac { 3 } { 200 }$, so $R = \frac { 200 } { 3 } \approx 66.7 \Omega$.
   Take the full CSCA Physics April 2026 Past Paper — timed & graded