Let’s solve each problem step by step.
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Practice Problem 4.1
We are told:
- Force (F) = 20 Newtons
- Charge (q) = 8.0 × 10⁻² C
We need to find the electric field intensity (E).
The formula is:
E = F / q
Plug in the numbers:
E = 20 N / (8.0 × 10⁻² C)
= 20 / 0.08
= 250 N/C
But 250 can be written as
2.5 × 10² N/C
Looking at the options:
a) 4.0 × 10⁻³ N/C
b) 1.6 N/C
c) 20 N/C
d) 2.5 × 10² N/C ← This matches!
✔ So, answer for 4.1 is
d
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Practice Problem 4.2
We are told:
- Force (F) = 4.0 × 10⁻¹⁰ N
- The charge is a proton → charge of proton = 1.6 × 10⁻¹⁹ C
Formula again:
E = F / q
Plug in:
E = (4.0 × 10⁻¹⁰) / (1.6 × 10⁻¹⁹)
= (4.0 / 1.6) × 10⁻¹⁰ ⁻ ⁽⁻¹⁹⁾
= 2.5 × 10⁹ N/C
Check options:
a) 6.4 × 10⁻²⁹
b) 1.6 × 10⁻¹⁹
c) 4.0 × 10⁻¹⁰
d) 2.5 × 10⁹ ← Correct!
✔ So, answer for 4.2 is
d
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Practice Problem 4.3
We are told:
- Electric field (E) = 3.0 × 10³ N/C
- Charge is “one elementary charge” → that’s the charge of a proton or electron = 1.6 × 10⁻¹⁹ C
We need to find force (F).
Formula:
F = E × q
Plug in:
F = (3.0 × 10³) × (1.6 × 10⁻¹⁹)
= (3.0 × 1.6) × 10³ ⁻ ¹⁹
= 4.8 × 10⁻¹⁶ N
Check options:
a) 1.0 × 10³
b) 1.6 × 10⁻¹⁹
c) 3.0 × 10³
d) 4.8 × 10⁻¹⁶ ← Correct!
✔ So, answer for 4.3 is
d
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Final Answer:
4.1: d
4.2: d
4.3: d
Parent Tip: Review the logic above to help your child master the concept of electrostatics worksheet.
